check-package-builds: switch to other spec to shorten CI build time

Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.com>

Author: cheeyanglee

.github/workflows/check-package-builds.yml

@@ -8,8 +8,8 @@
 name: Package build checks
 
 env:
-  REGULAR_PKG: kernel
-  REGULAR_PKG_SPEC_PATH: SPECS/kernel/kernel.spec
+  REGULAR_PKG: ca-certificates
+  REGULAR_PKG_SPEC_PATH: SPECS/ca-certificates/ca-certificates.spec
   TOOLCHAIN_PKG: xz
 
 on: