Revert "Tweak RuntimeInit docs around MimeMap registration."

This reverts commit 098a533e78.

Reason for revert: Base CL caused slower app startup (I don't know why).

Change-Id: Ib67852b900ff2baeb34f5d553fb0d233f5475888

core/java/com/android/internal/os/RuntimeInit.java

@@ -214,10 +214,7 @@ public class RuntimeInit {
         RuntimeHooks.setTimeZoneIdSupplier(() -> SystemProperties.get("persist.sys.timezone"));
 
         /*
-         * Replace libcore's minimal default mapping between MIME types and file
-         * extensions with a mapping that's suitable for Android. Android's mapping
-         * contains many more entries that are derived from IANA registrations but
-         * with several customizations (extensions, overrides).
+         * Set a default mapping between MIME types and file extensions.
          */
         MimeMap.setDefault(MimeMapImpl.createDefaultInstance());