Manual:$wgResourceLoaderMaxQueryLength

Details
ResourceLoader will not generate URLs whose query string is more than this many characters long and will instead use multiple requests with shorter query strings.

This degrades performance, but may be needed based on the maximum length supported by your web server and/or your user's web browsers.

Prior to MediaWiki 1.34, this could be set to a negative number, for which ResourceLoader would assume there is no query string length limit.

When installing MediaWiki, the installer will automatically warn if you have  installed with a limit lower than 2000.