PEP 1: Add a missing word in "Submitting a PEP" (#3311)

Author: tiangolo

pep-0001.txt

@@ -207,7 +207,7 @@ The standard PEP workflow is:
   It also provides a complete introduction to reST markup that is used
   in PEPs.  Approval criteria are:
 
-  * It sound and complete.  The ideas must make technical sense.  The
+  * It is sound and complete.  The ideas must make technical sense.  The
     editors do not consider whether they seem likely to be accepted.
   * The title accurately describes the content.
   * The PEP's language (spelling, grammar, sentence structure, etc.)