"No vulnerabilities found" message when using only-fixed: true

When using the `only-fixed: true` flag, if vulnerabilities are found, but ignored, the log message states...

```
No vulnerabilities found
```
...which implies there are no vulnerability concerns.

However, iff vulnerabilities are found and ignored, a more accurate message would be...

```
No vulnerabilities (that have a fix available) found
```
... as this wording matches the documentation for the `only-fixed` flag.

Please could this wording change be considered 👍.

Start by locating the `No vulnerabilities found` log message and the handling of the `only-fixed: true` flag in the scan-action repository. Confirm the wording used when vulnerabilities exist but are ignored because no fix is available; done means that case is clearly distinguished from finding no vulnerabilities.

Written by the indexing model from the issue text.