[liftoff] Remove dead method

The {TierUpFunction} method is unused after https://crrev.com/c/3275570.

R=jkummerow@chromium.org

Bug: v8:12281
Change-Id: I81882a6f1907ff3f4504dea8e9e307cbd674e682
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3306980Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78181}

src/wasm/baseline/liftoff-compiler.cc

@@ -771,11 +771,6 @@ class LiftoffCompiler {
     return false;
   }
 
-  void TierUpFunction(FullDecoder* decoder) {
-    __ CallRuntimeStub(WasmCode::kWasmTriggerTierUp);
-    DefineSafepoint();
-  }
-
   void TraceFunctionEntry(FullDecoder* decoder) {
     CODE_COMMENT("trace function entry");
     __ SpillAllRegisters();