Import: use contains() instead of count() where possible

src/Mod/Import/App/dxf/ImpExpDxf.cpp

@@ -189,7 +189,7 @@ bool ImpExpDxfRead::OnReadBlock(const std::string& name, int flags)
         // and don't want to be complaining about unhandled entity types.
         // Note that if it *is* for a hatch we could actually import it and use it to draw a hatch.
     }
-    else if (Blocks.count(name) > 0) {
+    else if (Blocks.contains(name)) {
         ImportError("Duplicate block name '%s'\n", name);
     }
     else {

src/Mod/Import/App/dxf/dxf.cpp

@@ -2689,7 +2689,7 @@ bool CDxfRead::ReadSection()
 }
 void CDxfRead::ProcessLayerReference(CDxfRead* object, void* target)
 {
-    if (object->Layers.count(object->m_record_data) == 0) {
+    if (!object->Layers.contains(object->m_record_data)) {
         object->ImportError("First reference to missing Layer '%s'", object->m_record_data);
         // Synthesize the Layer so we don't get the same error again.
         // We need to take copies of the string arguments because MakeLayer uses them as move