IR Optimizer failed to remove inline assembly code after ``return``

## Description

For the following contract
```solidity
pragma solidity ^0.8.0;

contract UnreachableCode {
uint256 globalVar = 10;

function foo(uint256 x) public {
if (x < 5) {
for (uint i = 0; i < 3; i++) {
globalVar = globalVar + i;
}
} else if (x < 10) {
while (globalVar > 0) {
globalVar = globalVar - 1;
if (globalVar == 5) {
break;
}
}
} else {
return;
}

return ;
unreachableCode();
}

function unreachableCode() private pure {
uint256 y = 5;
return ;
assembly {
let ptr := mload(0x40)
mstore(ptr, y)
}
}
}
```
The optimizer failed to remove the
```solidity
assembly {
let ptr := mload(0x40)
mstore(ptr, y)
}
```
## Environment

- Compiler version: 0.8.19
- Framework/IDE (e.g. Truffle or Remix):Remix
- Compiler config
```json
{
"language": "Solidity",
"settings": {
"viaIR": true,
"optimizer": {
"enabled": true,
"runs": 200
},
"outputSelection": {
"*": {
"": ["ast"],
"*": ["abi", "metadata", "devdoc", "userdoc", "storageLayout", "evm.legacyAssembly", "evm.bytecode", "evm.deployedBytecode", "evm.methodIdentifiers", "evm.gasEstimates", "evm.assembly"]
}
}
}
}
```

Reproduce the provided UnreachableCode contract with Solidity 0.8.19, viaIR, and the enabled optimizer. Inspect the generated IR and assembly outputs selected in the configuration, focusing on the code after return in unreachableCode(). Done means the optimizer removes the inline assembly after the return while preserving the rest of the generated output.

Written by the indexing model from the issue text.