pip: update edk2-pytool-extensions requirement from ~=0.27.2 to ~=0.2…

…7.3 (#753)

Updates the requirements on
[edk2-pytool-extensions](https://github.com/tianocore/edk2-pytool-extensions)
to permit the latest version.

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pip-requirements.txt

@@ -13,7 +13,7 @@
 ##
 
 edk2-pytool-library~=0.21.3 # MU_CHANGE
-edk2-pytool-extensions~=0.27.2 # MU_CHANGE
+edk2-pytool-extensions~=0.27.3 # MU_CHANGE
 antlr4-python3-runtime==4.13.1
 regex
 lcov-cobertura==2.0.2