Fix CLI usage text typo ("OPION" → "OPTION")

The CLI usage text for both commands contains a typo where "OPTION" is misspelled as "OPION".

**Files:**
- `cmd/tar-diff/main.go:19`
- `cmd/tar-patch/main.go:16`

**Current:**
```
Usage: tar-diff [OPION] old.tar.gz new.tar.gz result.tardiff
```

**Expected:**
```
Usage: tar-diff [OPTION] old.tar.gz new.tar.gz result.tardiff
```