Rollup merge of #108599 - nikic:drop-init, r=cuviper

Remove legacy PM leftovers

This drops two leftovers of legacy PM usage:
 * We don't need to initialize passes anymore.
 * The pass listing was still using legacy PM passes. Replace it with the corresponding new PM listing.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1814,8 +1814,6 @@ extern "C" {
     /// Creates a legacy pass manager -- only used for final codegen.
     pub fn LLVMCreatePassManager<'a>() -> &'a mut PassManager<'a>;
 
-    pub fn LLVMInitializePasses();
-
     pub fn LLVMTimeTraceProfilerInitialize();
 
     pub fn LLVMTimeTraceProfilerFinishThread();