doc: replace "practise" with "practice" in Documentation

To keep the Documentation consistent either
"practise" or "practice" should be used.

Since there are 3 lines with "practise"

  ~/linux/Documentation$ grep -r practise * | wc -l
  3

and 108 lines with "practice"

  ~/linux/Documentation$ grep -r practice * | wc -l
  108

this patch converts "practise" to "practice".

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index 26b1e31d..04c1edd 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -369,13 +369,13 @@
 	[lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
 	Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
 
-This practise is particularly helpful if you maintain a stable branch and
+This practice is particularly helpful if you maintain a stable branch and
 want at the same time to credit the author, track changes, merge the fix,
 and protect the submitter from complaints. Note that under no circumstances
 can you change the author's identity (the From header), as it is the one
 which appears in the changelog.
 
-Special note to back-porters: It seems to be a common and useful practise
+Special note to back-porters: It seems to be a common and useful practice
 to insert an indication of the origin of a patch at the top of the commit
 message (just after the subject line) to facilitate tracking. For instance,
 here's what we see in 2.6-stable :