build: not relying on gax's zip archive (#1273)

gax-java is now part of gapic-generator-java. No need to fetch
the released zip file to get the dependencies list.

In future, we'll revisit how we maintain the dependencies to
the user of gapic-generator-java, even for self-service users.

WORKSPACE

@@ -6,13 +6,9 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 # gapic-generator-java dependencies to match the order in googleapis repository,
 # which in its turn, prioritizes actual generated clients runtime dependencies
 # over the generator dependencies.
-
-_gax_java_version = "2.19.0"
-
-http_archive(
-    name = "com_google_api_gax_java",
-    strip_prefix = "gax-java-%s" % _gax_java_version,
-    urls = ["https://github.com/googleapis/gax-java/archive/v%s.zip" % _gax_java_version],
+local_repository(
+   name = "com_google_api_gax_java",
+   path = "gax-java",
 )
 
 load("@com_google_api_gax_java//:repository_rules.bzl", "com_google_api_gax_java_properties")