DOC: remove release process description from published documentation

It is not relevant for the users and takes precious space in the
documentation index, which is getting quite long.

Author: dnicolodi

docs/contributing/release-process.rst renamed to RELEASE.rst

@@ -2,12 +2,8 @@
 ..
 .. SPDX-License-Identifier: MIT
 
-
-.. _contributing-release-process:
-
-***************
 Release Process
-***************
+===============
 
 All releases are PGP signed with one of the keys listed in the
 `installation page`_. Before releasing please make sure your PGP key is listed
@@ -63,6 +59,3 @@ After that is done, you may release the project by following these steps:
 
 If you have any questions, please look at previous releases and/or ping the
 other maintainers.
-
-
-.. _installation page: installation

docs/contributing/index.rst

@@ -100,7 +100,6 @@ the use of ``meson-python`` and Meson for Python packaging.
 
    changelog
    about
-   contributing/index
    Discussions <https://github.com/mesonbuild/meson-python/discussions>
    Source Code <https://github.com/mesonbuild/meson-python>
    Issue Tracker <https://github.com/mesonbuild/meson-python/issues>