ISnippetProvider: Code polish

Remove useless constructors and destructors and consistently apply override/final.

Change-Id: I83d8e75803caa9007454b528f555a11a7930aefc
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/qmljseditor/qmljssnippetprovider.cpp

@@ -41,13 +41,6 @@
 using namespace QmlJSEditor;
 using namespace Internal;
 
-QmlJSSnippetProvider::QmlJSSnippetProvider() :
-    TextEditor::ISnippetProvider()
-{}
-
-QmlJSSnippetProvider::~QmlJSSnippetProvider()
-{}
-
 QString QmlJSSnippetProvider::groupId() const
 {
     return QLatin1String(Constants::QML_SNIPPETS_GROUP_ID);