[1.6.x] Various documentation typo/spelling fixes

Errors detected by Topy (https://github.com/intgr/topy), all changes
verified by hand.

Backport of 11d453bcad from master

docs/internals/committers.txt

@@ -321,7 +321,7 @@ Ramiro Morales
 
 Honza Král
     Honza first discovered Django in 2006 and started using it right away,
-    first for school and personal projects and later in his full time job. He
+    first for school and personal projects and later in his full-time job. He
     contributed various patches and fixes mostly to the newforms library,
     newforms admin and, through participation in the Google Summer of Code
     project, assisted in creating the :ref:`model validation
@@ -520,11 +520,10 @@ Marc Tamlyn
     documentation at DjangoCon EU 2012, and also helped to develop `CCBV`_, an
     additional class based view reference tool.
 
-    Marc currently works at `Incuna Ltd`_, a digital healthcare agency in
+    Marc is currently a full-time parent, part-time developer, and lives in
     Oxford, UK.
 
 .. _CCBV: http://ccbv.co.uk/
-.. _Incuna Ltd: http://incuna.com/
 
 Baptiste Mispelon
     Baptiste discovered Django around the 1.2 version and promptly switched away

docs/internals/contributing/writing-documentation.txt

@@ -192,7 +192,7 @@ Our policy for new features is:
     release, not the development version.
 
 Our preferred way for marking new features is by prefacing the features'
-documentation with: "``.. versionadded:: X.Y``", followed by a a mandatory
+documentation with: "``.. versionadded:: X.Y``", followed by a mandatory
 blank line and an optional content (indented).
 
 General improvements, or other changes to the APIs that should be emphasized