Reverting Protobuf version, due to conflict deps.

Previously the constraints were `tensorflow-metadata 1.17.1 depends on protobuf<4.22 and >=4.21.6; python_version < "3.11"` due to which the version 4.21.12, worked, but seems like the updated restrictions make it a conflicting change. So, reverting the protobuf version.

PiperOrigin-RevId: 776696513

Author: RecML authors

requirements.txt

@@ -63,7 +63,7 @@ platformdirs==4.3.7
 pluggy==1.5.0
 pre-commit==4.2.0
 promise==2.3
-protobuf==4.21.12
+protobuf==5.29.4
 psutil==7.0.0
 pyarrow==19.0.1
 pygments==2.19.1