Bug 943276 - Remove unused nsIPlatfromCharset. r=emk

By bug 1261841, we don't use nsIPlatfromCharset on PluginTags.  So we should remove unused header.

MozReview-Commit-ID: 8Y4YwRzTJuk

dom/plugins/base/nsPluginTags.cpp

@@ -11,7 +11,6 @@
 #include "nsPluginsDir.h"
 #include "nsPluginHost.h"
 #include "nsIBlocklistService.h"
-#include "nsIPlatformCharset.h"
 #include "nsPluginLogging.h"
 #include "nsNPAPIPlugin.h"
 #include "nsCharSeparatedTokenizer.h"