contrib/scripts: Remove special handling for patch release number 90

In commit 56dfec2 ("contrib/scripts: Support patch releases in
print-downgrade-version.sh"), we added support to disaply the previous
patch release for a given version number to the
print-downgrade-version.sh script. We treated to patch release values as
special cases: 0, because this means that we don't have a previous patch
release on the branch, and 90, because it used to be a temporary value
used during release processes.

But as Joe commented, we no longer use this "90" convention, but we use
something like vX.Y.Z-dev instead. Let's remove the reverence to 90 from
the script (and the workflow calling it).

Comparing with the commit introducing the special cases in the script,
the output remains nearly the same as when it was introduced, only the
previous patch release for "1.13.90" naturally turns to "1.13.89"
instead of providing an error.

        VERSION         Previous minor  Previous patch release

        1.14.3          v1.13           v1.14.2
        1.14.1          v1.13           v1.14.0
        1.14.0          v1.13           <error>
        1.14.1-dev      v1.13           v1.14.0
        1.15.0-dev      v1.14           <error>
        1.13.90         v1.12           v1.13.89

Reported-by: Joe Stringer <joe@cilium.io>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>

.github/workflows/tests-ipsec-upgrade.yaml

@@ -173,12 +173,8 @@ jobs:
           else
             # Upgrade from / downgrade to patch release.
             # In some cases we expect to fail to get the version number, do not
-            # fail the workflow in such case. This includes:
-            # - on main branch where we don't have preceeding patch releases
-            # - on stable branches on top of release preparation commits, where
-            #   we bump the patch version number to 90 and we can't easily
-            #   derive the number of the previous patch release version from
-            #   that.
+            # fail the workflow in such case. This is typically the case on
+            # main branch where we don't have preceeding patch releases.
             CILIUM_DOWNGRADE_VERSION=$(contrib/scripts/print-downgrade-version.sh patch || true)
             # Pass an empty tag to the cilium-config action to fall back to the
             # default release image, without crafting an image path with the

contrib/scripts/print-downgrade-version.sh

@@ -20,8 +20,7 @@ fi
 if [[ ${1-} == "patch" ]] ; then
     # If user passed "patch" as first argument, print the latest patch version
     case ${patch} in
-        0|90)
-            # Patch release number 90 is used for preparing releases.
+        0)
             >&2 echo "ERROR: failed to deduce patch release previous to version '$VERSION'"
             exit 1
             ;;