remove link to apc documentation

Author: MrYamous

performance.rst

@@ -91,7 +91,7 @@ Use the OPcache Byte Code Cache
 OPcache stores the compiled PHP files to avoid having to recompile them for
 every request. There are some `byte code caches`_ available, but as of PHP
 5.5, PHP comes with `OPcache`_ built-in. For older versions, the most widely
-used byte code cache is `APC`_.
+used byte code cache is APC.
 
 .. _performance-use-preloading:
 
@@ -347,7 +347,6 @@ Learn more
 .. _`byte code caches`: https://en.wikipedia.org/wiki/List_of_PHP_accelerators
 .. _`OPcache`: https://www.php.net/manual/en/book.opcache.php
 .. _`Composer's autoloader optimization`: https://getcomposer.org/doc/articles/autoloader-optimization.md
-.. _`APC`: https://www.php.net/manual/en/book.apc.php
 .. _`APCu Polyfill component`: https://github.com/symfony/polyfill-apcu
 .. _`APCu PHP functions`: https://www.php.net/manual/en/ref.apcu.php
 .. _`cachetool`: https://github.com/gordalina/cachetool