.ci/check_unsupported.sh: Skip bear dependencies

Many of the bear dependencies are unable to be installed
on older unsupported versions of Python. The unsupported
tests objective is to verify that irrespective of any
other failure to install, coala-bears has its own check
to prevent running on older versions. Hence skipping the
installation of bear dependencies ensures the check
still works even if other packages dont break first.

Closes coala#2488
Related to coala#2611

.ci/check_unsupported.sh

@@ -8,8 +8,8 @@ set -o pipefail
 
 set -x
 
-# mypy-lang and guess-language-spirit do not install on unsupported versions
-sed -i.bak -E '/^(mypy-lang|guess-language-spirit)/d' bear-requirements.txt
+# Many bear dependencies do not install on unsupported versions
+echo "" > bear-requirements.txt
 
 python setup.py install | tee setup.log