Move protovalidate to optional and dev dependencies

protovalidate is only used in tests and for optional validation
functionality. Moving it out of required dependencies reduces the
install footprint for users who don't need validation. It remains
available via the 'validation' optional extra (pip install
authzed[validation]) and in the dev dependency group for testing.

Signed-off-by: ivanauth <ivan@authzed.com>

Author: ivanauth

pyproject.toml

@@ -19,11 +19,16 @@ dependencies = [
   "protobuf>=5.26,<7",
   "grpc-interceptor>=0.15.4,<0.16",
   "googleapis-common-protos>=1.65.0,<2",
+]
+
+[project.optional-dependencies]
+validation = [
   "protovalidate>=0.7.1,<1.2.0",
 ]
 
 [dependency-groups]
 dev = [
+  "protovalidate>=0.7.1,<1.2.0",
   "grpc-stubs~=1.53",
   "grpcio-tools>=1.63,<1.79",
   "mypy==1.19.1",