[Filesystem] fixed exception message when not a able to write to a directory

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

This simply fixes an exception message in the Filesystem Component when a directory is not writable while dumping a file via `dumpFile()`.