ci(miri): Turn off Miri PowerPC64 job

The job currently fails, seemingly due to some caching issue, on a Pull
Request for dependency updates supposed to fix CI, so it's blocking us
from testing in CI and merging things at the moment. Let's disable it
until the issue is sorted.

Cc: @daniel-noland
Link: https://github.com/githedgehog/dataplane/actions/runs/28030274103/job/82968910470?pr=1603
Signed-off-by: Quentin Monnet <qmo@qmon.net>

Author: qmonnet

.github/workflows/dev.yml

@@ -325,12 +325,17 @@ jobs:
       - *tmate
 
   miri:
-    if: >-
-      ${{
-        needs.check_changes.outputs.devfiles == 'true'
-        || startsWith(github.event.ref, 'refs/tags/v')
-        || github.event_name == 'workflow_dispatch'
-      }}
+    ## FIXME: The only job from the matrix (powerpc64) currently disabled
+    ## because we faced a caching issue (it seems?), and it's blocking CI.
+    ## See https://github.com/githedgehog/dataplane/actions/runs/28030274103/job/82968910470?pr=1603
+    ## Revert disabling once the issue is solved.
+    #if: >-
+    #  ${{
+    #    needs.check_changes.outputs.devfiles == 'true'
+    #    || startsWith(github.event.ref, 'refs/tags/v')
+    #    || github.event_name == 'workflow_dispatch'
+    #  }}
+    if: false
     name: "check/miri/${{ matrix.cpu }}"
     runs-on: "lab"
     needs: