SUSE-SU-2023:1702-1 Security update for shim

This update for shim fixes the following issues: - Updated shim signature after shim 15.7 be signed back: signature-sles.x8664.asc, signature-sles.aarch64.asc bsc1198458 - Add POSTPROCESSPEFLAGS=-N to the build command in shim.spec to disable the NX compatibility flag when using post-process-pe...