chore(bazel): update protobuf to v3.21.3

chore(bazel): update gax-java to 2.18.4

PiperOrigin-RevId: 463115700

WORKSPACE

@@ -47,9 +47,9 @@ http_archive(
 
 http_archive(
     name = "com_google_protobuf",
-    sha256 = "8b28fdd45bab62d15db232ec404248901842e5340299a57765e48abe8a80d930",
-    strip_prefix = "protobuf-3.20.1",
-    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.20.1.tar.gz"],
+    sha256 = "c29d8b4b79389463c546f98b15aa4391d4ed7ec459340c47bffe15db63eb9126",
+    strip_prefix = "protobuf-3.21.3",
+    urls = ["https://github.com/protocolbuffers/protobuf/archive/v3.21.3.tar.gz"],
 )
 
 load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
@@ -216,7 +216,7 @@ maven_install(
     ],
 )
 
-_gax_java_version = "2.18.1"
+_gax_java_version = "2.18.4"
 
 http_archive(
     name = "com_google_api_gax_java",