api-test.t: set a default method

Dependencies

• [2] GLJD3PG2 api-test.t: make it work under yath
• [3] LZVO64YG Merge in the first bits of the API work

Change contents

• replacement in t/api-test.t at line 45
  [2.859]→[2.859:937](∅→∅)
  − $req->header(Origin => "http://localhost/") if $opts->{method} eq "POST";
  [2.859]

  [2.937]
  + $req->header(Origin => "http://localhost/") if ($opts->{method} // "") eq "POST";