Add RHEL 9.4 to merge job (#30)

Co-authored-by: Bart Thomee <11445373+bthomee@users.noreply.github.com>

Author: bthomee

.github/workflows/rhel.yml

@@ -136,12 +136,18 @@ jobs:
     strategy:
       matrix:
         os:
+          - release: 9.4
+            compiler_name: gcc
+            compiler_version: 12
           - release: 9.6
             compiler_name: gcc
             compiler_version: 13
           - release: 9.6
             compiler_name: gcc
             compiler_version: 14
+          - release: 9.4
+            compiler_name: clang
+            compiler_version: 'any'
           - release: 9.6
             compiler_name: clang
             compiler_version: 'any'