Remove unnecessary cast from LLVMRustGetInstrProfIncrementIntrinsic

This particular cast appears to have been copied over from clang, but there are
plenty of other call sites in clang that don't bother with a cast here, and it
works fine without one.

For context, `llvm::Intrinsic::ID` is a typedef for `unsigned`, and
`llvm::Intrinsic::instrprof_increment` is a member of
`enum IndependentIntrinsics : unsigned`.

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1524,8 +1524,8 @@ extern "C" LLVMValueRef LLVMRustBuildCall(LLVMBuilderRef B, LLVMTypeRef Ty, LLVM
 }
 
 extern "C" LLVMValueRef LLVMRustGetInstrProfIncrementIntrinsic(LLVMModuleRef M) {
-  return wrap(llvm::Intrinsic::getDeclaration(unwrap(M),
-              (llvm::Intrinsic::ID)llvm::Intrinsic::instrprof_increment));
+  return wrap(llvm::Intrinsic::getDeclaration(
+      unwrap(M), llvm::Intrinsic::instrprof_increment));
 }
 
 extern "C" LLVMValueRef LLVMRustBuildMemCpy(LLVMBuilderRef B,