Document how to suppress colorized output and summary line

Fixes #7439.

Author: tapaswenipathak

docs/source/config_file.rst

@@ -401,6 +401,11 @@ section of the command line docs.
 ``show_column_numbers`` (bool, default False)
     Shows column numbers in error messages.
 
+``color_output`` (bool, default True)
+    Shows error messages with no color.
+
+``error_summary`` (bool, default True)
+    Shows error messages without any stats summary.
 
 Advanced options
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