Documentation: fix misuses of "nor"

Signed-off-by: Justin Lebar <jlebar@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/howto/rebase-from-internal-branch.txt

@@ -139,7 +139,7 @@ You fetch from upstream, but not merge.
     $ git fetch upstream
 
 This leaves the updated upstream head in .git/FETCH_HEAD but
-does not touch your .git/HEAD nor .git/refs/heads/master.
+does not touch your .git/HEAD or .git/refs/heads/master.
 You run "git rebase" now.
 
     $ git rebase FETCH_HEAD master

Documentation/howto/revert-a-faulty-merge.txt

@@ -54,7 +54,7 @@ where C and D are to fix what was broken in A and B, and you may already
 have some other changes on the mainline after W.
 
 If you merge the updated side branch (with D at its tip), none of the
-changes made in A nor B will be in the result, because they were reverted
+changes made in A or B will be in the result, because they were reverted
 by W.  That is what Alan saw.
 
 Linus explains the situation:
@@ -90,7 +90,7 @@ with:
     $ git revert W
 
 This history would (ignoring possible conflicts between what W and W..Y
-changed) be equivalent to not having W nor Y at all in the history:
+changed) be equivalent to not having W or Y at all in the history:
 
  ---o---o---o---M---x---x-------x----
 	       /

Documentation/howto/revert-branch-rebase.txt

@@ -137,7 +137,7 @@ $ make clean test ;# make sure it did not cause other breakage.
 ------------------------------------------------
 
 Everything is in the good order.  I do not need the temporary branch
-nor tag anymore, so remove them:
+or tag anymore, so remove them:
 
 ------------------------------------------------
 $ rm -f .git/refs/tags/pu-anchor