[FIX] github.search_migration_pr: fix matching of module name in PR title

[sebalix]

The PR title is split by words without including special characters (this doesn't include _).

Before this change, the term to match against could have been my_module:, e.g.:

$ oca-port 14.0 16.0 stock_warehouse_flow --output=json | jq .
{
  "process": "migrate",
  "results": {}
}

With this change, the term to match become my_module:

$ oca-port 14.0 16.0 stock_warehouse_flow --output=json | jq .
{
  "process": "migrate",
  "results": {
    "existing_pr": {
      "url": "https://github.com/OCA/wms/pull/704",
      "ref": "OCA/wms#704",
      "author": "RodrigoBM",
      "title": "[16.0][MIG] stock_warehouse_flow: Migration to 16.0",
      "merged_at": "",
      "number": 704
    }
  }
}

[simahawk]

tests ❤️