Remove google_clockwork list of soong plugins

The only plugin in that list has been removed.

Bug: 307824623
Test: Presubmits
Change-Id: Ieceb8610cfb2425500659a009703895a4f499cb1
diff --git a/android/plugin.go b/android/plugin.go
index 2c7f9ff..d62fc94 100644
--- a/android/plugin.go
+++ b/android/plugin.go
@@ -72,7 +72,6 @@
 
 var internalPluginsPaths = []string{
 	"vendor/google/build/soong/internal_plugins.json",
-	"vendor/google_clockwork/build/internal_plugins.json",
 }
 
 type pluginProvider interface {