Infrastructure: switch to our qt-orderedmap fork (Mudlet#5812)

#### Brief overview of PR changes/additions
Until mandeepsandhu/qt-ordered-map#29 is accepted, lets switch to our fork which has the fix.
#### Motivation for adding to Mudlet
Remove the tens of messages like this we get while compiling:

```
[39/74] Building CXX object src/CMakeFiles/mudlet.dir/TDockWidget.cpp.o
In file included from /media/vadi/SSDer/Programs/Mudlet/src/TDockWidget.cpp:21:
In file included from /media/vadi/SSDer/Programs/Mudlet/src/TDockWidget.h:23:
In file included from /media/vadi/SSDer/Programs/Mudlet/src/mudlet.h:70:
/media/vadi/SSDer/Programs/Mudlet/src/../3rdparty/qt-ordered-map/src/orderedmap.h:118:11: warning: class member cannot be redeclared [-Wredeclared-class-member]
    class const_iterator;
          ^
/media/vadi/SSDer/Programs/Mudlet/src/../3rdparty/qt-ordered-map/src/orderedmap.h:47:11: note: previous declaration is here
    class const_iterator;
          ^
1 warning generated.
```