Pagination does not work when using sort_by in search query language

When using the following query through the webapp search interface with search query language option enabled: origin: github and sort_by = [-last_visit], the first page of result is correctly displayed but when requesting the next page the following error is returned:

{
   "error":{
      "root_cause":[
         {
            "type":"illegal_argument_exception",
            "reason":"search_after has 2 value(s) but sort has 3."
         }
      ],
      "type":"search_phase_execution_exception",
      "reason":"all shards failed",
      "phase":"query",
      "grouped":true,
      "failed_shards":[
         {
            "shard":0,
            "index":"origin-v0.11",
            "node":"gz-GX7OwRdqPMWGYVrmXtw",
            "reason":{
               "type":"illegal_argument_exception",
               "reason":"search_after has 2 value(s) but sort has 3."
            }
         }
      ],
      "caused_by":{
         "type":"illegal_argument_exception",
         "reason":"search_after has 2 value(s) but sort has 3.",
         "caused_by":{
            "type":"illegal_argument_exception",
            "reason":"search_after has 2 value(s) but sort has 3."
         }
      }
   },
   "status":400
}```

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*Migrated from T4296 ([view on Phabricator](https://forge.softwareheritage.org/T4296))*