Update reference to tests/phpunit/phpunit.php

Bug: T90875
Change-Id: Ieee9a9bd8b24e42815fdbf98d374b54e084c8e9e

README

@@ -24,10 +24,10 @@ users input ($tex). The equation is displayed in the current text line.
 {\displaystyle $tex } to the user input ($tex).
 
 For testing your installation run
-php tests/phpunit/phpunit.php extensions/Math/tests/
+composer phpunit:entrypoint -- extensions/Math/tests/phpunit/
 from your MediaWiki home path.
 
 == Logging ==
 The math extension supports PSR-3 logging:
 Configuration can be dona via
-$wgDebugLogGroups['Math'] = [ 'level' => 'info', 'destination' => '/path/to/file.log' ];
+$wgDebugLogGroups['Math'] = [ 'level' => 'info', 'destination' => '/path/to/file.log' ];