Revert header comment in dune-project.

Zimmi48 · web-flow · commit 6d0eada4299c · 2020-12-16T17:57:18.000+01:00
This is actually not allowed by Dune.
diff --git a/dune-project.mustache b/dune-project.mustache
@@ -1,6 +1,3 @@
-; This file was generated from `meta.yml`, please do not edit manually.
-; Follow the instructions on https://github.com/coq-community/templates to regenerate.
-
 (lang dune 2.5)
 (using coq 0.2)
 (name {{ shortname }})
