chore: update psalm.xml

See #125 (comment)

Author: kenjis

psalm.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0"?>
 <psalm
+    phpVersion="8.1"
     errorLevel="7"
     resolveFromConfigFile="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
@@ -8,6 +9,8 @@
     autoloader="psalm_autoload.php"
     cacheDirectory="build/psalm/"
     errorBaseline="psalm-baseline.xml"
+    findUnusedBaselineEntry="false"
+    findUnusedCode="false"
 >
     <projectFiles>
         <directory name="src/" />