pip: update edk2-pytool-library requirement from ~=0.21.3 to ~=0.21.4

Updates the requirements on [edk2-pytool-library](https://github.com/tianocore/edk2-pytool-library) to permit the latest version.
- [Release notes](https://github.com/tianocore/edk2-pytool-library/releases)
- [Commits](tianocore/edk2-pytool-library@v0.21.3...v0.21.4)

---
updated-dependencies:
- dependency-name: edk2-pytool-library
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

pip-requirements.txt

@@ -12,7 +12,7 @@
 # https://www.python.org/dev/peps/pep-0440/#version-specifiers
 ##
 
-edk2-pytool-library~=0.21.3
+edk2-pytool-library~=0.21.4
 edk2-pytool-extensions~=0.27.3
 antlr4-python3-runtime==4.13.1
 regex==2023.12.25