fix: validation error when AAD manifest does not contain accessToken property

[blackchoey]

fix validation error when AAD manifest does not contain accessToken property in optionalClaims

https://msazure.visualstudio.com/Microsoft%20Teams%20Extensibility/_workitems/edit/27212864

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.19%. Comparing base (e00bf86) to head (ed3dbd2).
Report is 7 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #11131      +/-   ##
==========================================
+ Coverage   87.16%   87.19%   +0.02%     
==========================================
  Files         457      457              
  Lines       27638    27640       +2     
  Branches     5561     5554       -7     
==========================================
+ Hits        24092    24100       +8     
  Misses       1778     1778              
+ Partials     1768     1762       -6     

Files	Coverage Δ
.../component/driver/aad/utility/aadManifestHelper.ts	83.33% <100.00%> (ø)

... and 1 file with indirect coverage changes