git-gui: MERGE_RR lives in .git/ directly with newer Git versions

Now that MERGE_RR was moved out of .git/rr-cache/, we have to delete
it somewhere else.  Just in case somebody wants to use a newer git-gui
with an older Git, the file .git/rr-cache/MERGE_RR is removed, too (if
it exists).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/merge.tcl

@@ -257,6 +257,7 @@ proc _reset_wait {fd} {
 
 		catch {file delete [gitdir MERGE_HEAD]}
 		catch {file delete [gitdir rr-cache MERGE_RR]}
+		catch {file delete [gitdir MERGE_RR]}
 		catch {file delete [gitdir SQUASH_MSG]}
 		catch {file delete [gitdir MERGE_MSG]}
 		catch {file delete [gitdir GITGUI_MSG]}