[#4793] Very minor tweak that sounds more natural

Author: weaverryan

contributing/documentation/format.rst

@@ -11,7 +11,7 @@ reStructuredText
 reStructuredText is a plaintext markup syntax similar to Markdown, but much
 stricter with its syntax. If you are new to reStructuredText, take some time to
 familiarize with this format by reading the existing `Symfony documentation`_
-in raw format.
+source code.
 
 If you want to learn more about this format, check out the `reStructuredText Primer`_
 tutorial and the `reStructuredText Reference`_.