gpl-1.0-plus false positive

### Description

The GPL-2.0-or later at:

https://github.com/plougher/squashfs-tools/blob/master/squashfs-tools/mksquashfs.c#L6561

is not succesfully detected:

```
{
"license_expression": "gpl-1.0-plus",
"license_expression_spdx": "GPL-1.0-or-later",
"from_file": "mksquashfs.c",
"start_line": 6561,
"end_line": 6570,
"matcher": "3-seq",
"score": 98.68,
"matched_length": 75,
"match_coverage": 98.68,
"rule_relevance": 100,
"rule_identifier": "gpl-1.0-plus_461.RULE",
"rule_url": "https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/gpl-1.0-plus_461.RULE"
}

```