Fix protoc search path in setup.py (#14318)

This PR is fixing small inconsistencies in the paths where the protobuf compiler is searched for in the protobuf python setup.py.

Closes #14318

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/14318 from ottmar-zittlau:main 598d13406f
PiperOrigin-RevId: 573315569

python/setup.py

@@ -35,9 +35,9 @@ elif os.path.exists('../bazel-bin/protoc'):
   protoc = '../bazel-bin/protoc'
 elif os.path.exists('../bazel-bin/protoc.exe'):
   protoc = '../bazel-bin/protoc.exe'
-elif os.path.exists('protoc'):
+elif os.path.exists('../protoc'):
   protoc = '../protoc'
-elif os.path.exists('protoc.exe'):
+elif os.path.exists('../protoc.exe'):
   protoc = '../protoc.exe'
 elif os.path.exists('../vsprojects/Debug/protoc.exe'):
   protoc = '../vsprojects/Debug/protoc.exe'