FindVulkan: Restore tolerance of unknown FATAL_ERROR component

`find_package(Vulkan REQUIRED FATAL_ERROR)` calls exist in the wild, but
`find_package` does not have a `FATAL_ERROR` option.  We silently
tolerated such calls prior to commit 6e4d20921d (FindVulkan: Add
component for `shaderc_combined`, 2022-05-18, v3.24.0-rc1~111^2~5), by
treating the argument as a component and ignoring it.  Restore tolerance
by removing the component and warning about it.

Fixes: #23849