Drop 'quicktions' dependency

With e3ee75a
the source code already changed to only optionally support 'quicktions',
but otherwise to always use 'fractions'. Unfortunately some mutwo
packages relied on mutwo.core >= 1 < 2 to install quicktions for them
[1], [2]. Due to this dropping quicktions in mutwo.core < 2 would have
broke certain dependencies. We therefore only drop this now in
mutwo.core v.2.0.0.

[1] mutwo-org/mutwo.music@ba8a290
[2] mutwo-org/mutwo.abjad@af2d8c3

setup.py

@@ -32,7 +32,6 @@
     install_requires=[
         "numpy>=1.18, <2.00",
         "python-ranges>=1.2.0, <2.0.0",
-        "quicktions>=1.10, <2.0",
     ],
     extras_require=extras_require,
     classifiers=[