Remove unused variable CachedResourceLoader::m_loadFinishing

Remove unused variable CachedResourceLoader::m_loadFinishing
https://bugs.webkit.org/show_bug.cgi?id=84100

Reviewed by Alexey Proskuryakov.

No new tests, removing dead code.

* loader/cache/CachedResourceLoader.cpp:
(WebCore::CachedResourceLoader::CachedResourceLoader):
(WebCore::CachedResourceLoader::loadDone):
(WebCore::CachedResourceLoader::decrementRequestCount):
* loader/cache/CachedResourceLoader.h:
(CachedResourceLoader):
(WebCore::CachedResourceLoader::requestCount):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114328 268f45cc-cd09-0410-ab3c-d52691b4dbfc