Lowercase XPKG repo name to avoid xpkg push failure

Otherwise it will fail for GitHub orgs with uppercase chars in theri
name with the error similar to the one below

```
crossplane: error: failed to parse package tag "xpkg.upbound.io/UpboundCare/function-azresourcegraph:v0.0.0-20241211161841-62aad247be2c": repository can only contain the characters `abcdefghijklmnopqrstuvwxyz0123456789_-./`: UpboundCare/function-azresourcegraph
```

Signed-off-by: Yury Tsarev <[email protected]>

Author: ytsarev

.github/workflows/ci.yml

@@ -164,4 +164,6 @@ jobs:
 
       - name: Push Multi-Platform Package to Upbound
         if: env.XPKG_ACCESS_ID != ''
-        run: "./crossplane --verbose xpkg push --package-files $(echo *.xpkg|tr ' ' ,) ${{ env.XPKG }}:${{ env.XPKG_VERSION }}"
+        # XPKG repo name can't contain uppercase characters like UpboundCare, we need to lowercase if the GithubOrg contains them.
+        # See https://github.com/orgs/community/discussions/25768#discussioncomment-8057564 for XPKG@L lowercase explanation
+        run: "./crossplane --verbose xpkg push --package-files $(echo *.xpkg|tr ' ' ,) ${XPKG@L}:${{ env.XPKG_VERSION }}"