github CI: upgrade to omnetpp-6.3 -- this makes the single fingerprint failure go away

simulations/nr/mec/singleMecHost/ -f omnetpp.ini -c BgGeneratorApp -r 0
 (some fingerprint mismatch: actual '91b8-f45e/tplx;fb39-a929/~tNl', expected: '03c5-ba51/tplx;86a6-e080/~tNl')

It ONLY materialized inside CI, in MODE=debug, and with omnetpp-6.2. Change any,
and it will go away. I.e. not reproducible outside CI.

Use new local-debug.yml workflow on your local machine with the nektos/act tool
(https://github.com/nektos/act) to reproduce it.

Author: avarga

.github/workflows/fingerprint-tests.yml

@@ -29,7 +29,7 @@ jobs:
         with:
           repository: omnetpp/omnetpp
           path: omnetpp
-          ref: omnetpp-6.2.0
+          ref: omnetpp-6.3.0
 
       - name: Checking out INET
         uses: actions/checkout@v4