change capitalization of suggested error messages

Author: adqm

peps/pep-0798.rst

@@ -336,13 +336,13 @@ cases:
       File "<stdin>", line 1
         [*x if x else y]
          ^^^^^^^^^^^^^^
-    SyntaxError: invalid starred expression.  did you forget to wrap the conditional expression in parentheses?
+    SyntaxError: invalid starred expression. Did you forget to wrap the conditional expression in parentheses?
 
      >>> {**x if x else y}
       File "<stdin>", line 1
         {**x if x else y}
          ^^^^^^^^^^^^^^^
-    SyntaxError: invalid double starred expression.  did you forget to wrap the conditional expression in parentheses?
+    SyntaxError: invalid double starred expression. Did you forget to wrap the conditional expression in parentheses?
 
     >>> [x if x else *y]
       File "<stdin>", line 1