Remove rpm-plugin-ima in Dockerfile on F41

This plugin of ours, when installed in a container, currently causes
transaction errors (simply because IMA isn't supported in containers
currently).

This isn't immediately visible unless we'd run a second dnf transaction
in the Dockerfile but it's just unnecessary, we don't need the plugin
for anything.

The reason it's installed is through the ima-evm-utils-devel package
(which pulls in ima-evm-utils-libs which pulls in the plugin).  This is
a new thing on F41 so only handle it there.

tests/Dockerfile.fedora

@@ -64,7 +64,11 @@ RUN ln -sf $(rpm --eval '%{_target_platform}%{?_gnu}')-pkg-config \
            /usr/bin/pkg-config
 
 # Self-destruct stock rpm
-RUN if ! which dnf5; then \
+RUN if which dnf5; then \
+        # Fedora 41+ \
+        rpm -e --nodeps --nodb \
+            rpm-plugin-ima; \
+    else \
         # Fedora 40 \
         rpm -e --nodeps --nodb \
             rpm-sign-libs \