pip: bump edk2-pytool-extensions from 0.26.3 to 0.26.4

Bumps [edk2-pytool-extensions](https://github.com/tianocore/edk2-pytool-extensions) from 0.26.3 to 0.26.4.
- [Release notes](https://github.com/tianocore/edk2-pytool-extensions/releases)
- [Commits](tianocore/edk2-pytool-extensions@v0.26.3...v0.26.4)

---
updated-dependencies:
- dependency-name: edk2-pytool-extensions
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pip-requirements.txt

@@ -13,7 +13,7 @@
 ##
 
 edk2-pytool-library==0.19.8
-edk2-pytool-extensions==0.26.3
+edk2-pytool-extensions==0.26.4
 edk2-basetools==0.1.49
 antlr4-python3-runtime==4.13.1
 xmlschema==2.5.0