Fix Apache functions return types to reflect the stubs (#4076)

This was already the case in PHP 7.

reference/apache/functions/apache-request-headers.xml

@@ -27,8 +27,7 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   An associative array of all the HTTP headers in the current request, or
-   &false; on failure.
+   An associative array of all the HTTP headers in the current request.
   </para>
  </refsect1>
 

reference/apache/functions/apache-response-headers.xml

@@ -10,7 +10,7 @@
  <refsect1 role="description">
   &reftitle.description;
   <methodsynopsis>
-   <type class="union"><type>array</type><type>false</type></type><methodname>apache_response_headers</methodname>
+   <type>array</type><methodname>apache_response_headers</methodname>
    <void/>
   </methodsynopsis>
   <para>
@@ -27,7 +27,7 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   An array of all Apache response headers on success&return.falseforfailure;.
+   An array of all Apache response headers on success.
   </para>
  </refsect1>
  

reference/apache/functions/getallheaders.xml

@@ -31,8 +31,7 @@
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
   <para>
-   An associative array of all the HTTP headers in the current request, or
-   &false; on failure.
+   An associative array of all the HTTP headers in the current request.
   </para>
  </refsect1>