chore(deps): update dependency protobuf to v6 (#8133)

Author: renovate-bot

.kokoro/docs/docker/requirements.txt

@@ -139,18 +139,16 @@ proto-plus==1.25.0 \
     # via
     #   -r requirements.in
     #   google-api-core
-protobuf==4.25.4 \
-    --hash=sha256:051e97ce9fa6067a4546e75cb14f90cf0232dcb3e3d508c448b8d0e4265b61c1 \
-    --hash=sha256:0dc4a62cc4052a036ee2204d26fe4d835c62827c855c8a03f29fe6da146b380d \
-    --hash=sha256:3319e073562e2515c6ddc643eb92ce20809f5d8f10fead3332f71c63be6a7040 \
-    --hash=sha256:4c8a70fdcb995dcf6c8966cfa3a29101916f7225e9afe3ced4395359955d3835 \
-    --hash=sha256:7e372cbbda66a63ebca18f8ffaa6948455dfecc4e9c1029312f6c2edcd86c4e1 \
-    --hash=sha256:90bf6fd378494eb698805bbbe7afe6c5d12c8e17fca817a646cd6a1818c696ca \
-    --hash=sha256:ac79a48d6b99dfed2729ccccee547b34a1d3d63289c71cef056653a846a2240f \
-    --hash=sha256:ba3d8504116a921af46499471c63a85260c1a5fc23333154a427a310e015d26d \
-    --hash=sha256:bfbebc1c8e4793cfd58589acfb8a1026be0003e852b9da7db5a4285bde996978 \
-    --hash=sha256:db9fd45183e1a67722cafa5c1da3e85c6492a5383f127c86c4c4aa4845867dc4 \
-    --hash=sha256:eecd41bfc0e4b1bd3fa7909ed93dd14dd5567b98c941d6c1ad08fdcab3d6884b
+protobuf==6.30.2 \
+    --hash=sha256:0eb523c550a66a09a0c20f86dd554afbf4d32b02af34ae53d93268c1f73bc65b \
+    --hash=sha256:35c859ae076d8c56054c25b59e5e59638d86545ed6e2b6efac6be0b6ea3ba048 \
+    --hash=sha256:4f6c687ae8efae6cf6093389a596548214467778146b7245e886f35e1485315d \
+    --hash=sha256:50f32cc9fd9cb09c783ebc275611b4f19dfdfb68d1ee55d2f0c7fa040df96815 \
+    --hash=sha256:524afedc03b31b15586ca7f64d877a98b184f007180ce25183d1a5cb230ee72b \
+    --hash=sha256:7653c99774f73fe6b9301b87da52af0e69783a2e371e8b599b3e9cb4da4b12b9 \
+    --hash=sha256:acec579c39c88bd8fbbacab1b8052c793efe83a0a5bd99db4a31423a25c0a0e2 \
+    --hash=sha256:ae86b030e69a98e08c77beab574cbcb9fff6d031d57209f574a5aea1445f4b51 \
+    --hash=sha256:b12ef7df7b9329886e66404bef5e9ce6a26b54069d7f7436a0853ccdeb91c103
     # via
     #   gcp-docuploader
     #   google-api-core