Do not collect expanded detected license texts on binaries

[pombredanne]

For gosu binaries, and this license text: license: GPL-3 (full text at https://github.com/tianon/gosu), and $ scancode -l --license-text gosu --json-pp - we get this long (truncated here for brevity) "junk":

"files": [
    {
      "path": "gosu",
      "type": "file",
      "licenses": [
        {
          "key": "gpl-3.0",
          "score": 16.0,
          "name": "GNU General Public License 3.0",
          "short_name": "GPL 3.0",
          "category": "Copyleft",
          "is_exception": false,
          "owner": "Free Software Foundation (FSF)",
          "homepage_url": "http://www.gnu.org/licenses/gpl-3.0.html",
          "text_url": "http://www.gnu.org/licenses/gpl-3.0-standalone.html",
          "reference_url": "https://enterprise.dejacode.com/urn/urn:dje:license:gpl-3.0",
          "spdx_license_key": "GPL-3.0-only",
          "spdx_url": "https://spdx.org/licenses/GPL-3.0-only",
          "start_line": 3980,
          "end_line": 3980,
          "matched_rule": {
            "identifier": "gpl-3.0_rdesc_1.RULE",
            "license_expression": "gpl-3.0",
            "licenses": [
              "gpl-3.0"
            ],
            "is_license_text": false,
            "is_license_notice": false,
            "is_license_reference": false,
            "is_license_tag": true,
            "matcher": "2-aho",
            "rule_length": 3,
            "matched_length": 3,
            "match_coverage": 100.0,
            "rule_relevance": 16
          },
          "matched_text": "> (den<<shift)/2unsupported compression for {{%s %s}}%s{{else}}%s{{end}} cannot be converted to type 45474735088646411895751953125LockOSThread nesting overflowSIGPIPE: write to broken pipeSIGPWR: power failure restartTime.UnmarshalBinary: no dataaddspecial on invalid pointerbufio.Scanner: token too longcannot 3-index slice a stringexecuting on Go runtime stackgc done but gcphase != _GCoffgfput: bad status (not Gdead)invalid length of trace eventio: 
.
.
.
8495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899\nUsage: {{ .Self }} user-spec command [args]\n   eg: {{ .Self }} tianon bash\n       {{ .Self }} nobody:root bash -c 'whoami && id'\n       {{ .Self }} 1000:1 id\n\n{{ .Self }} version: {{ .Version }}\n{{ .Self }} license: GPL-3 (full text at https://github.com/tianon/gosu)"
        }
      ],
      "license_expressions": [
        "gpl-3.0"
      ],
      "percentage_of_license_text": 0.01,
      "scan_errors": []
    }
  ]
}