Remove pin of graphviz to 8 and disable yarpviz compilation on conda until YARP 3.10.0 is released

[traversaro]

The pin was added in #1538 as a workaround for #1537, as the proper fixes have been released, we should be able to just drop the pin and use graphviz 9, to avoid incompatibility with libraries that actually use graphviz 9.

[traversaro]

Fix #1602 .

[traversaro]

the proper fixes have been released

This is not true. robotology/yarp#3056 was merged, but was never released, and yarp-3.9 branch and yarp 3.9.0 tag still do not compile with graphviz 9. As graphviz is just used for yarpviz compilation, and as I think that ROS compatibility (see #1602) is more important, I think we can change the workaround to actually disable yarpviz on conda, and re-enable it once YARP 3.10 is released.

[traversaro]

Indeed, the build still fails, let's disable yarpviz compilation on conda instead.

[20/1300] Building CXX object extern/qgv/CMakeFiles/YARP_priv_qgvcore.dir/qgv/QGVCore/QGVScene.cpp.o
FAILED: extern/qgv/CMakeFiles/YARP_priv_qgvcore.dir/qgv/QGVCore/QGVScene.cpp.o 
/home/runner/miniconda3/envs/test/bin/x86_64-conda-linux-gnu-c++ -DBUILDING_YARP -DQGVCORE_LIB -DQT_CORE_LIB -DQT_GUI_LIB -DQT_NO_DEBUG -DQT_WIDGETS_LIB -I/home/runner/work/robotology-superbuild/robotology-superbuild/b/src/YARP/extern/qgv/YARP_priv_qgvcore_autogen/include -I/home/runner/miniconda3/envs/test/include/eigen3 -I/home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore -I/home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore/private -I/home/runner/work/robotology-superbuild/robotology-superbuild/b/src/YARP/extern/qgv -I/home/runner/miniconda3/envs/test/include/graphviz -isystem /home/runner/miniconda3/envs/test/include/qt -isystem /home/runner/miniconda3/envs/test/include/qt/QtWidgets -isystem /home/runner/miniconda3/envs/test/include/qt/QtGui -isystem /home/runner/miniconda3/envs/test/include/qt/QtCore -isystem /home/runner/miniconda3/envs/test/./mkspecs/linux-g++ -w -fvisibility-inlines-hidden -fmessage-length=0 -march=no
In file included from /home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore/QGVScene.cpp:27:
/home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore/private/QGVCore.h: In static member function 'static Agraph_t* QGVCore::agmemread2(const char*)':
/home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore/private/QGVCore.h:96:14: error: 'Agdisc_t' {aka 'struct Agdisc_s'} has no member named 'mem'
   96 |         disc.mem = &AgMemDisc;
      |              ^~~
/home/runner/work/robotology-superbuild/robotology-superbuild/src/YARP/extern/qgv/qgv/QGVCore/private/QGVCore.h:96:21: error: 'AgMemDisc' was not declared in this scope; did you mean 'AgIoDisc'?
   96 |         disc.mem = &AgMemDisc;
      |                     ^~~~~~~~~
      |                     AgIoDisc

[traversaro]

let's disable yarpviz compilation on conda instead.

Done in 03f7933 .