doc: minor whitespace, punctuation

Author: blueyed

doc/en/mark.rst

@@ -1,9 +1,7 @@
-
 .. _mark:
 
 Marking test functions with attributes
-=================================================================
-
+======================================
 
 By using the ``pytest.mark`` helper you can easily set
 metadata on your test functions. There are
@@ -164,4 +162,4 @@ More details can be found in the `original PR <https://github.com/pytest-dev/pyt
 .. note::
 
     in a future major relase of pytest we will introduce class based markers,
-    at which point markers will no longer be limited to instances of :py:class:`Mark`
+    at which point markers will no longer be limited to instances of :py:class:`Mark`.

doc/en/writing_plugins.rst

@@ -223,7 +223,6 @@ import ``helper.py`` normally.  The contents of
    pytest.register_assert_rewrite("pytest_foo.helper")
 
 
-
 Requiring/Loading plugins in a test module or conftest file
 -----------------------------------------------------------