MutexContainer is only used mixin-style in derived classes

...no need for virtual dtor

Change-Id: I843e4bbb8bab3ed1eec55be2b937617175911162
Reviewed-on: https://gerrit.libreoffice.org/72049
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

chart2/source/inc/MutexContainer.hxx

@@ -27,10 +27,11 @@ namespace chart
 
 class OOO_DLLPUBLIC_CHARTTOOLS MutexContainer
 {
-public:
-    virtual ~MutexContainer();
-
 protected:
+    MutexContainer() = default;
+
+    ~MutexContainer() = default;
+
     mutable ::osl::Mutex m_aMutex;
 
     ::osl::Mutex & GetMutex() const;

chart2/source/tools/MutexContainer.cxx

@@ -22,9 +22,6 @@
 namespace chart
 {
 
-MutexContainer::~MutexContainer()
-{}
-
 ::osl::Mutex & MutexContainer::GetMutex() const
 {
     return m_aMutex;