Replace invalid PHPDoc @return type boolean with bool

Summary: `@return boolean` is not a valid type thus use `@return bool`.

Test Plan: None.

Reviewers: O1 Blessed Committers, valerio.bozzolan

Reviewed By: O1 Blessed Committers, valerio.bozzolan

Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno

Differential Revision: https://we.phorge.it/D25795

src/infrastructure/parser/PhutilURIHelper.php

@@ -69,7 +69,7 @@ final class PhutilURIHelper extends Phobject {
   /**
    * Check whenever the URI starts with the provided character.
    * @param string $char String that MUST have length of 1.
-   * @return boolean
+   * @return bool
    */
   private function isStartingWithChar($char) {
     return strncmp($this->uriStr, $char, 1) === 0;