ci: bypass v1 registries.conf in opm catalog render (#241)

opm v1.72.0 (bumped from v1.68.0 in #240) ships a newer containers/image
that dropped v1->v2 auto-conversion of registries.conf and hard-errors on
the ubuntu-latest runner's v1-format /etc/containers/registries.conf,
breaking `opm alpha render-template` in the catalog build.

Point CONTAINERS_REGISTRIES_CONF at /dev/null so the lib uses built-in
defaults; fully-qualified ghcr.io bundle pulls need no registries config.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: GrigoryPervakov

Makefile

@@ -598,7 +598,7 @@ catalog-template: # Generate catalog template with all bundles from registry
 
 .PHONY: catalog-render
 catalog-render: opm catalog-template ## Generate FBC catalog from template
-	$(OPM) alpha render-template catalog/clickhouse-operator-template.yaml > catalog/catalog.yaml
+	CONTAINERS_REGISTRIES_CONF=/dev/null $(OPM) alpha render-template catalog/clickhouse-operator-template.yaml > catalog/catalog.yaml
 	$(OPM) validate catalog
 
 .PHONY: catalog-build