Replace LLVMRustContextCreate with normal LLVM-C API calls

Since `LLVMRustContextCreate` can easily be replaced with a call to
`LLVMContextCreate` and `LLVMContextSetDiscardValueNames`.

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -123,12 +123,6 @@ extern "C" void LLVMRustSetLastError(const char *Err) {
   LastError = strdup(Err);
 }
 
-extern "C" LLVMContextRef LLVMRustContextCreate(bool shouldDiscardNames) {
-  auto ctx = new LLVMContext();
-  ctx->setDiscardValueNames(shouldDiscardNames);
-  return wrap(ctx);
-}
-
 extern "C" void LLVMRustSetNormalizedTarget(LLVMModuleRef M,
                                             const char *Target) {
 #if LLVM_VERSION_GE(21, 0)