matrix: demote fedora40 to x86_64 only

problem: building the fedora40 arm64 container takes too long. Even at 6
jobs, it takes over two hours, and is blocking other containers from
getting tagged

solution: demote fedora40 to x86_64 only

Author: trws

.github/workflows/main.yml

@@ -254,7 +254,7 @@ jobs:
         echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
         docker manifest create fluxrm/flux-core:bookworm fluxrm/flux-core:bookworm-amd64 fluxrm/flux-core:bookworm-386 fluxrm/flux-core:bookworm-arm64
         docker manifest push fluxrm/flux-core:bookworm
-        for d in el9 noble fedora40 alpine ; do
+        for d in el9 noble alpine ; do
           docker manifest create fluxrm/flux-core:$d fluxrm/flux-core:$d-amd64 fluxrm/flux-core:$d-arm64
           docker manifest push fluxrm/flux-core:$d
         done

src/test/generate-matrix.py

@@ -217,14 +217,6 @@ def __str__(self):
         TEST_INSTALL="t",
     ),
 )
-matrix.add_multiarch_build(
-    name="fedora40",
-    default_suffix=" - test-install",
-    args=common_args,
-    env=dict(
-        TEST_INSTALL="t",
-    ),
-)
 matrix.add_multiarch_build(
     name="alpine",
     default_suffix=" - test-install",
@@ -241,6 +233,14 @@ def __str__(self):
 )
 
 # single arch builds that still produce a container
+matrix.add_build(
+    name="fedora40 - test-install",
+    args=common_args,
+    env=dict(
+        TEST_INSTALL="t",
+    ),
+    docker_tag=True,
+)
 # Ubuntu: TEST_INSTALL
 matrix.add_build(
     name="jammy - test-install",