Add a couple more pure annotations

src/Psalm/Internal/PhpVisitor/PartialParserVisitor.php

@@ -325,6 +325,9 @@ class PartialParserVisitor extends PhpParser\NodeVisitorAbstract implements PhpP
         return $this->must_rescan || $this->non_method_changes;
     }
 
+    /**
+     * @psalm-pure
+     */
     private function balanceBrackets(string $fake_class) : string
     {
         $tokens = \token_get_all($fake_class);

src/Psalm/Internal/PluginManager/ComposerLock.php

@@ -23,7 +23,10 @@ class ComposerLock
 
     /**
      * @param mixed $package
+     *
      * @psalm-assert-if-true array $package
+     *
+     * @psalm-pure
      */
     public function isPlugin($package): bool
     {