Revert "Default to building with OpenJDK 9 -target 1.8."

After this revert CL topic, the default toolchain for Android
goes back to being OpenJDK 8.

This revert is being prepared ahead of time in case of
any problems with original change topic,
https://r.android.com/#/q/topic:bug_69449021

Bug: 69449021
Test: Treehugger

This reverts commit 0ae8b548af38c8b8fccea7cdef11d54740d3bb6a.

Change-Id: Ief7646a94f1a264085cd299b4327d244b78a1537
diff --git a/android/config.go b/android/config.go
index f806b49..0eebb5f 100644
--- a/android/config.go
+++ b/android/config.go
@@ -295,10 +295,7 @@
 func (c *config) fromEnv() error {
 	switch c.Getenv("EXPERIMENTAL_USE_OPENJDK9") {
 	case "":
-		if c.Getenv("RUN_ERROR_PRONE") != "true" {
-			// Use OpenJDK9, but target 1.8
-			c.useOpenJDK9 = true
-		}
+		// Use OpenJDK8
 	case "false":
 		// Use OpenJDK8
 	case "1.8":
@@ -309,7 +306,7 @@
 		c.useOpenJDK9 = true
 		c.targetOpenJDK9 = true
 	default:
-		return fmt.Errorf(`Invalid value for EXPERIMENTAL_USE_OPENJDK9, should be "", "false", "1.8", or "true"`)
+		return fmt.Errorf(`Invalid value for EXPERIMENTAL_USE_OPENJDK9, should be "", "1.8", or "true"`)
 	}
 
 	return nil