Typofix in Makefile comment.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Makefile

@@ -33,7 +33,7 @@ all:
 # Define NO_SYMLINK_HEAD if you never want .git/HEAD to be a symbolic link.
 # Enable it on Windows.  By default, symrefs are still used.
 #
-# Define NO_SVN_TESTS if you want to skip time-consuming SVN interopability
+# Define NO_SVN_TESTS if you want to skip time-consuming SVN interoperability
 # tests.  These tests take up a significant amount of the total test time
 # but are not needed unless you plan to talk to SVN repos.
 #