Correct case of error message

.. so that it's the same in both universal.c and pod/perldiag.pod.  This
enables us to preserve status of universal.c in t/porting/diag.t.

Per: Tony Cook review.

Author: jkeenan

pod/perldiag.pod

@@ -1340,7 +1340,7 @@ C<require> function does not know what to do with the object.
 See also L<perlfunc/require>.
 
 =item Attempt to call undefined %s method with arguments via package
-"%s" (perhaps you forgot to load the package?)
+"%s" (Perhaps you forgot to load the package?)
 
 (F) You called the C<import()> or C<unimport()> method of a class that has no
 such method defined in its inheritance graph, and passed an argument to the

t/porting/diag.t

@@ -251,7 +251,7 @@ my $specialformats_re = qr/%$format_modifiers"\s*($specialformats)(\s*(?:"|\z))?
 my @include_xs_files = (
   "builtin.c",
   "class.c",
-  #"universal.c",
+  "universal.c",
 );
 
 if (@ARGV) {