Revert "Renaming .gitk-new to .gitk fails if there is already a .gitk."

This reverts commit 3a8b35c3e3

A quick test showed that this is unnecessary.  Unfortunately,
the commit message does not explain the specific reason for
the patch.  It could be issues with FAT or Windows shares.
We hope that this is fixed since we switched to Tcl/Tk 8.5.5.

gitk-git/gitk

@@ -2568,7 +2568,6 @@ proc savestuff {w} {
 	}
 	puts $f "}"
 	close $f
-	catch {file delete "~/.gitk"}
 	file rename -force "~/.gitk-new" "~/.gitk"
     }
     set stuffsaved 1