Enhance recognition subset of the matched_text is detected, and prevent returning `unknown-license-reference`

```
- matches:
- score: '100.0'
matcher: 2-aho
end_line: 4449
rule_url: https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/lead-in_unknown_30.RULE
from_file:
start_line: 4448
matched_text: |
• The ‘libunistring’ library and its header files are dual-licensed
under "the GNU LGPLv3+ or the GNU GPLv2+". This means, you can use
match_coverage: '100.0'
matched_length: 3
rule_relevance: 100
rule_identifier: lead-in_unknown_30.RULE
license_expression: unknown-license-reference
license_expression_spdx: LicenseRef-scancode-unknown-license-reference
- score: '100.0'
matcher: 2-aho
end_line: 4449
rule_url: https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/lgpl-3.0-plus_74.RULE
from_file:
start_line: 4449
matched_text: ' under "the GNU LGPLv3+ or the GNU GPLv2+". This means, you can use'
match_coverage: '100.0'
matched_length: 2
rule_relevance: 100
rule_identifier: lgpl-3.0-plus_74.RULE
license_expression: lgpl-3.0-plus
license_expression_spdx: LGPL-3.0-or-later
- score: '100.0'
matcher: 2-aho
end_line: 4449
rule_url: https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/gpl-2.0-plus_488.RULE
from_file:
start_line: 4449
matched_text: ' under "the GNU LGPLv3+ or the GNU GPLv2+". This means, you can use'
match_coverage: '100.0'
matched_length: 2
rule_relevance: 100
rule_identifier: gpl-2.0-plus_488.RULE
license_expression: gpl-2.0-plus
license_expression_spdx: GPL-2.0-or-later
```

As the `matched_text` contains 2 lines and the second line have license detected alright, it may make sense if the matched_text only contains the first line: `The ‘libunistring’ library and its header files are dual-licensed` and return `unknown-license-reference`. However, as it also includes the second line `under "the GNU LGPLv3+ or the GNU GPLv2+". The tool should be able to tell this 2 lines are detected alright and not to return `unknown-license-reference`