lang/clover: remove llvm:max=16 restriction, part 2

Follow-up on ports e4b79a0e4ebe, by entirely removing the dependency on
libLLVMSPIRVLib.so.${LLVM_VERSION}. This also makes it possible to bump
LLVM_DEFAULT to a higher value, for bug 283013.

PR: 280957
Approved by: maintainer timeout (2 weeks)
MFH: 2025Q1