Renaming a file with flow errors, changing only its case, leaves errors behind associated with old file name

The basic issue is that after running flow and finding errors in a file, renaming that file in a way that only changes the case of the filename can leave you stuck with those errors.

To reproduce:
1) Create a file Multiply.js
```
// @flow
const multiply = (x, y) => {
return x * y;
};

multiply(2, 3);
multiply(4, "five");
```
2) Run flow to see error
```
Multiply.js:3
3: return x * y;
^ string. The operand of an arithmetic operation must be a number.
```
3) Change the file name, case-only, to multiply.js
4) Run flow again, which results in errors reported for both the old and new names
```
Multiply.js:3
3: return x * y;
^ string. The operand of an arithmetic operation must be a number.

multiply.js:3
3: return x * y;
^ string. The operand of an arithmetic operation must be a number.
```
5) Delete multiply.js
6) Run flow again, which continues to show the error for Multiply.js even though it doesn't exist anymore
```
Multiply.js:3
string. The operand of an arithmetic operation must be a number.
```

At this point, you can get the error to go away by creating an empty Multiply.js file and running flow again, but I couldn't find any other way in the docs to clear what flow had remembered about errors in this file.