tools: Use a consistent target name when building mariner initrd

Currently a mixture of cbl-mariner and mariner is used when creating the
mariner initrd. The kata-static tarball has mariner in the name, but the
jenkins url uses cbl-mariner. This breaks cache usage.

Use mariner as the target name throughout the build, so that caching works.

Fixes: #7292
Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>

versions.yaml

@@ -159,7 +159,7 @@ assets:
       x86_64:
         name: *default-initrd-name
         version: *default-initrd-version
-        cbl-mariner:
+        mariner:
           name: "cbl-mariner"
           version: "2.0"
         sev: