Remove legacy repo_name settings (#3772)

I'd kept these in to separate the bazel module update from the BUILD
file changes, then forgot about it. I think all of these can be cleanly
removed now. I think it's something we should clean up for consistency
with the bazel central repository names; I think it's best to reduce
that divergence.

llvm_zlib and llvm_zstd remain because of how llvm depends on the
particular names.

migrate_cpp/cpp_refactoring/BUILD

@@ -39,7 +39,7 @@ cc_library(
     hdrs = ["matcher_test_base.h"],
     deps = [
         ":matcher",
-        "@com_google_googletest//:gtest",
+        "@googletest//:gtest",
         "@llvm-project//clang:ast_matchers",
         "@llvm-project//clang:tooling",
         "@llvm-project//clang:tooling_core",
@@ -66,7 +66,7 @@ cc_test(
         ":fn_inserter",
         ":matcher_test_base",
         "//testing/base:gtest_main",
-        "@com_google_googletest//:gtest",
+        "@googletest//:gtest",
         "@llvm-project//clang:tooling",
     ],
 )
@@ -89,7 +89,7 @@ cc_test(
         ":for_range",
         ":matcher_test_base",
         "//testing/base:gtest_main",
-        "@com_google_googletest//:gtest",
+        "@googletest//:gtest",
         "@llvm-project//clang:tooling",
     ],
 )
@@ -114,7 +114,7 @@ cc_test(
         ":matcher_test_base",
         ":var_decl",
         "//testing/base:gtest_main",
-        "@com_google_googletest//:gtest",
+        "@googletest//:gtest",
         "@llvm-project//clang:tooling",
     ],
 )