ci: remove obsolete comment

Signed-off-by: Martin Kröning <martin.kroening@eonerc.rwth-aachen.de>

.github/workflows/build.yml

@@ -1,9 +1,3 @@
-# Based on https://github.com/actions-rs/meta/blob/master/recipes/quickstart.md
-#
-# While our "example" application has the platform-specific code,
-# for simplicity we are compiling and testing everything on the Ubuntu environment only.
-# For multi-OS testing see the `cross.yml` workflow.
-
 on: [push, pull_request]
 
 name: Build