GHA: Change label from s390x to s390x-large

Recently, an additional s390x runner was added to the organization.
However, it is insufficient for running the operator e2e tests and
will function as a supplementary builder.

This commit changes the label for the platform from s390x to s390x-large
to differentiate this runner.

Signed-off-by: Hyounggyu Choi <Hyounggyu.Choi@ibm.com>

.github/workflows/ccruntime-nightly.yaml

@@ -11,7 +11,7 @@ jobs:
       commit-hash: ${{ github.sha }}
 
   e2e-ibm-se-nightly:
-    runs-on: s390x
+    runs-on: s390x-large
     strategy:
       fail-fast: false
       matrix:

.github/workflows/ccruntime_e2e.yaml

@@ -24,7 +24,7 @@ jobs:
         instance:
           - "az-ubuntu-2004"
           - "az-ubuntu-2204"
-          - "s390x"
+          - "s390x-large"
           - "tdx"
           - "sev"
           - "sev-snp"