ToolChainManager: Do not try saving in ~ToolChainManager

This is after plugins have been shutdown. The toolchains are saved on
shutdown anyway.

Change-Id: I7d84c3c4538f27aa3f4c7c2677307de49621d641
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/projectexplorer/toolchainmanager.cpp

@@ -213,7 +213,6 @@ void ToolChainManager::restoreToolChains()
 
 ToolChainManager::~ToolChainManager()
 {
-    saveToolChains(); // Make sure to save tool chains when closing
     delete d;
     m_instance = 0;
 }