docs: submitting-patches - change non-ascii character to ascii

Documentation/process/submitting-patches.rst contains a non-ascii
character.  Change it to the ascii equivalent.

Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/submitting-patches.rst

@@ -413,7 +413,7 @@ e-mail discussions.
 
 
 
-11) Sign your work — the Developer's Certificate of Origin
+11) Sign your work - the Developer's Certificate of Origin
 ----------------------------------------------------------
 
 To improve tracking of who did what, especially with patches that can