remove poolManager test

[xvallspl]

Due to moving from TPoolManager to RTaskArena as an interface to
the TBB pool of threads.

See root-project/root#7065

[phsft-bot]

Starting build on ROOT-debian10-i386/cxx14, ROOT-performance-centos8-multicore/default, ROOT-fedora30/cxx14, ROOT-fedora31/noimt, ROOT-ubuntu16/nortcxxmod, mac1014/python3, mac11.0/cxx17, windows10/cxx14
How to customize builds

[phsft-bot]

Build failed on windows10/cxx14.
Running on null:C:\build\workspace\roottest-pullrequests-build
See console output.

Errors:

• [2021-01-20T12:37:01.088Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\PyROOTStrings.h(16,10): fatal error C1083: Cannot open include file: 'DllImport.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:01.423Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\PyROOTStrings.cxx(13,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:01.701Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\TMemoryRegulator.h(37,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:02.416Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\RPyROOTApplication.cxx(14,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:02.416Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\GenericPyz.cxx(14,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:02.416Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\RVecPyz.cxx(12,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:02.802Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\TClassPyz.cxx(13,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:02.802Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\TClonesArrayPyz.cxx(13,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:03.089Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\TDirectoryFilePyz.cxx(12,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]
• [2021-01-20T12:37:03.089Z] C:\build\workspace\roottest-pullrequests-build\root\bindings\pyroot\pythonizations\src\TDirectoryPyz.cxx(12,10): fatal error C1083: Cannot open include file: 'CPyCppyy.h': No such file or directory [C:\build\workspace\roottest-pullrequests-build\build\bindings\pyroot\pythonizations\ROOTPythonizations3_8.vcxproj]

And 11 more