fix: license check's false positive

Here is the license:
https://github.com/python-attrs/attrs/blob/24.3.0/LICENSE

However, the tool was reporting `UNKNOWN` license before authorizing it explicitly in the `strategy.ini`:
```
gathering licenses...
34 packages and dependencies.
check authorized packages...
33 packages.
check unknown packages...
1 package.
    attrs (24.3.0): UNKNOWN
      dependencies:
          attrs << jsonschema << open-aea
          attrs << pytest
```

strategy.ini

@@ -91,3 +91,5 @@ filelock: >=3.0.12
 fetchai-ledger-api: >=0.0.1
 chardet: >=3.0.4
 certifi: >=2019.11.28
+; licence is MIT, but the tool does not detect it
+attrs: ==24.3.0