[1.7.x] Fixed spelling mistake and added a word to the word list.

Backport of 1165e9992e from master

docs/releases/1.7.txt

@@ -1315,7 +1315,7 @@ than simply ``myapp/models.py``, Django would look for :ref:`initial SQL data
 will search ``myapp/sql/`` as documented. The old location will continue to
 work until Django 1.9. After this issue was fixed, migrations were added which
 deprecates initial SQL data. Thus, while this change still exists, the
-deprecation is somehwhat irrelevant as the entire feature will be removed in
+deprecation is somewhat irrelevant as the entire feature will be removed in
 Django 2.0 when migrations become compulsory for all applications.
 
 Reorganization of ``django.contrib.sites``

docs/spelling_wordlist

@@ -519,6 +519,7 @@ screenshots
 sdist
 semimajor
 semiminor
+serializability
 serializable
 serializer
 serializers