make punctuation consistent between generator examples

Author: adqm

peps/pep-0798.rst

@@ -1045,15 +1045,15 @@ Generator Cleanup with ``.close()``
         finally:
             print("outer generator received GeneratorExit")
 
-    # With yield from - GeneratorExit is passed through to sub-generator
+    # With yield from, GeneratorExit is passed through to sub-generator
     gen1 = yield_from()
     print(next(gen1))  # prints "first"
     gen1.close()  # closes sub-generator and then outer generator
 
-    # With explicit loop - GeneratorExit goes to outer generator first
+    # With explicit loop, GeneratorExit goes to outer generator only
     gen2 = explicit_loop()
     print(next(gen2))  # prints "first"
-    gen2.close()  #only closes outer generator
+    gen2.close()  # only closes outer generator
 
     print('program finished; GC will close the explicit loop subgenerator')
     # second inner generator closes when GC closes it at the end