fix Unix socket syntax

[leManu]

• Resolves: Socket syntax unclear for dbhost variable

Summary

See nextcloud/documentation#13173 (comment) for more explanations

[nickvergessen]

Matches the tests:

server/tests/lib/DB/ConnectionFactoryTest.php

Lines 15 to 27 in 3e7db01

	public static function splitHostFromPortAndSocketData(): array {
	return [
	['127.0.0.1', ['host' => '127.0.0.1']],
	['db.example.org', ['host' => 'db.example.org']],
	['unix', ['host' => 'unix']],
	['[::1]', ['host' => '[::1]']],
	['127.0.0.1:3306', ['host' => '127.0.0.1', 'port' => 3306]],
	['db.example.org:3306', ['host' => 'db.example.org', 'port' => 3306]],
	['unix:3306', ['host' => 'unix', 'port' => 3306]],
	['[::1]:3306', ['host' => '[::1]', 'port' => 3306]],
	['unix:/socket', ['host' => 'unix', 'unix_socket' => '/socket']],
	];
	}

[welcome]

Thanks for your first pull request and welcome to the community! Feel free to keep them coming! If you are looking for issues to tackle then have a look at this selection: https://github.com/nextcloud/server/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22