Build/Test tools use Trunk revision 2170172 of importer

Update Travis configuration to temporarily use trunk for the importer in order for PHP 7.4 tests to pass. When the new version is released, this will be updated to point to that tag.

See: #48231


Built from https://develop.svn.wordpress.org/trunk@46542


git-svn-id: https://core.svn.wordpress.org/trunk@46339 1a063a9b-81f0-0310-95a4-ce76da25c4cd