Fix PHPUnit deprecation

Author: timacdonald

phpunit.xml

@@ -13,11 +13,11 @@
             <directory>tests/Feature</directory>
         </testsuite>
     </testsuites>
-    <coverage>
+    <source>
         <include>
             <directory suffix=".php">src</directory>
         </include>
-    </coverage>
+    </source>
     <php>
         <env name="DB_CONNECTION" value="sqlite" />
         <env name="DB_DATABASE" value=":memory:" />