Delete check for EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9.

This has been a no-op for a year now. https://cs.android.com/android/_/android/platform/build/soong/+/a1c9e9da550e9b72a7ed9a442f98ece25650d5dc

Test: TH presubmit
Change-Id: Id9cc56045cbca4ebae64170e5443501b9ccc8260
diff --git a/android/config.go b/android/config.go
index d833c5c..4b2f40f 100644
--- a/android/config.go
+++ b/android/config.go
@@ -263,10 +263,6 @@
 
 	config.mockFileSystem(bp, fs)
 
-	if err := config.fromEnv(); err != nil {
-		panic(err)
-	}
-
 	return Config{config}
 }
 
@@ -436,10 +432,6 @@
 		config.AndroidFirstDeviceTarget = firstTarget(config.Targets[Android], "lib64", "lib32")[0]
 	}
 
-	if err := config.fromEnv(); err != nil {
-		return Config{}, err
-	}
-
 	if Bool(config.productVariables.GcovCoverage) && Bool(config.productVariables.ClangCoverage) {
 		return Config{}, fmt.Errorf("GcovCoverage and ClangCoverage cannot both be set")
 	}
@@ -487,17 +479,6 @@
 	c.mockBpList = blueprint.MockModuleListFile
 }
 
-func (c *config) fromEnv() error {
-	switch c.Getenv("EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9") {
-	case "", "true":
-		// Do nothing
-	default:
-		return fmt.Errorf("The environment variable EXPERIMENTAL_JAVA_LANGUAGE_LEVEL_9 is no longer supported. Java language level 9 is now the global default.")
-	}
-
-	return nil
-}
-
 func (c *config) StopBefore() bootstrap.StopBefore {
 	return c.stopBefore
 }