fixup grammar nit

Author: leonerd

pod/perldiag.pod

@@ -7529,8 +7529,7 @@ match any declared named parameter.  The caller of the subroutine is
 presumably at fault.
 
 This message may report multiple parameter names, if more than one name was
-passed that is does not match.  In that case it will use the word
-"parameters".
+passed that does not match.  In that case it will use the word "parameters".
 
 The message attempts to include the name of the called subroutine.  If
 the subroutine has been aliased, the subroutine's original name will be