[PATCH STABLE] update: fix typo in help text

[Adrian Buehlmann]

# HG changeset patch
# User Adrian Buehlmann <adrian at cadifra.com>
# Date 1344242711 -7200
# Branch stable
# Node ID 76907c3d8791213f12161fae31e50afe86e13bae
# Parent  b5c560787a4e61be322059fbaf6a2269bad6a917
update: fix typo in help text

Spotted by Kevin Chase <kevincha99 at hotmail.com>

diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -5772,7 +5772,7 @@
     current named branch and move the current bookmark (see :hg:`help
     bookmarks`).
 
-    Update sets the working directory's parent revison to the specified
+    Update sets the working directory's parent revision to the specified
     changeset (see :hg:`help parents`).
 
     If the changeset is not a descendant or ancestor of the working