DO NOT MERGE. Remove jdiff git config as it was added in master only.

Test: Studio does not complain when opening support library project.
Change-Id: I61b06a62b093a87622c72bc5903862f29b5c7f9b
(cherry picked from commit f3bfca73d440d99c79b043ba66581c44d046c4dc)
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index b24c09a..a4645bc 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -3,6 +3,5 @@
   <component name="VcsDirectoryMappings">
     <mapping directory="" vcs="Git" />
     <mapping directory="$PROJECT_DIR$/../../external/doclava" vcs="Git" />
-    <mapping directory="$PROJECT_DIR$/../../external/jdiff" vcs="Git" />
   </component>
-</project>
\ No newline at end of file
+</project>