Stop creating Download folder on start

The existence of this folder isn't required to run qbt and it can be
created when adding torrent.
Closes #8290.

src/base/profile.cpp

@@ -43,7 +43,6 @@ Profile::Profile(Private::Profile *impl, Private::PathConverter *pathConverter)
     ensureDirectoryExists(SpecialFolder::Cache);
     ensureDirectoryExists(SpecialFolder::Config);
     ensureDirectoryExists(SpecialFolder::Data);
-    ensureDirectoryExists(SpecialFolder::Downloads);
 }
 
 // to generate correct call to ProfilePrivate::~ProfileImpl()