Update docs/conventions.rst

Co-authored-by: bbhtt <[email protected]>

docs/conventions.rst

@@ -108,7 +108,7 @@ is used for their application launcher. These icons should be
 provided in accordance with the `Freedesktop icon specification
 <https://specifications.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html>`_.
 
-Icons should be named using the application's ID, be in either PNG or SVG
+Icons must be named using the application's ID, be in either PNG or SVG
 format, and must be placed in the standard location::
 
   /app/share/icons/hicolor/$size/apps/