adding infra to exclude patterns

This will remove infra from getting rendered by sphinx
Signed-off-by: Avinash Mehta <avinash.mehta@arm.com>

conf.py

@@ -36,7 +36,7 @@ templates_path = ['_templates']
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
 # This pattern also affects html_static_path and html_extra_path.
-exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store']
+exclude_patterns = ['_build', 'Thumbs.db', '.DS_Store', 'docs/infra']
 
 
 # -- Options for HTML output -------------------------------------------------