Bug 1598279 - Update docs of format.js to reflect in documentation. r=whimboo,marionette-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D54181

--HG--
rename : testing/marionette/doc/internals/format.js => testing/marionette/doc/internals/format.rst
extra : moz-landing-system : lando

testing/marionette/doc/internals/format.js

@@ -1,4 +0,0 @@
-format module
-=============
-.. js:autoclass:: format
-  :members:

testing/marionette/doc/internals/format.rst

@@ -0,0 +1,11 @@
+format module
+=============
+
+
+pprint
+------
+.. js:autofunction:: pprint
+
+truncate
+--------
+.. js:autofunction:: truncate