Stop verifying fs-verity signature in kernel

This has become redundant since we're now checking the signature in
userspace.

Bug: 258538225
Test: atest GtsFontHostTestCases
Test: atest UpdatableFontDirTest
Test: atest UpdatableSystemFontTest
Test: atest FontManagerTest
Change-Id: I18dc93e1b54b3ff97474113cd5689e7cc058e000
Merged-In: I18dc93e1b54b3ff97474113cd5689e7cc058e000