gn2bp: add back a comment

Comment was deleted during a previous refactoring step.

Test: none
Change-Id: I1f4d3d1915122bdaed65bfdc0c58e63a1f41d5d3
diff --git a/tools/gn2bp/gen_android_bp b/tools/gn2bp/gen_android_bp
index 8b0a943..10fc1a8 100755
--- a/tools/gn2bp/gen_android_bp
+++ b/tools/gn2bp/gen_android_bp
@@ -691,6 +691,7 @@
   # TODO: verify if it actually *is* universally applicable.
   def _sanitize_filepath(self, filepath):
     # Careful, order matters!
+    # delete all leading ../
     filepath = re.sub('^(\.\./)+', '', filepath)
     filepath = re.sub('^gen/jni_headers', '$(genDir)', filepath)
     filepath = re.sub('^gen', '$(genDir)', filepath)