Add support for QT 6.6.0

[VocalFan]

Is your feature request related to a problem? Please describe. I use Install Qt for my projects, which depends on aqtinstall... This project. I've noticed that 6.6.0 seems to not be supported right now.

Describe the solution you'd like Implementation of support for Qt 6.6.0

Describe alternatives you've considered None that I have found so far...

Additional context

C:\hostedtoolcache\windows\Python\3.11.4\x64\python.exe -m aqt install-qt windows desktop 6.* win64_msvc2019_64 --outputdir D:\a\obliteration/Qt
INFO    : aqtinstall(aqt) v3.1.6 on Python 3.11.4 [CPython MSC v.1934 64 bit (AMD64)]
INFO    : Resolved spec '6.*' to 6.6.0
WARNING : Specified Qt version "6.6.0" did not exist when this version of aqtinstall was released. This may not install properly, but we will try our best.
ERROR   : Failed to locate XML data for Qt version '6.6.0'.
==============================Suggested follow-up:==============================
* Please use 'aqt list-qt windows desktop' to show versions available.
Error: Error: The process 'C:\hostedtoolcache\windows\Python\3.11.4\x64\python.exe' failed with exit code 1

[miurahr]

6.6.0-Beta2 Release is in 14.07.2023 and final release is in 10.10.2023. The bug ticket is raised in 14, Jul when the Qt Foundation published the 6.6.0-Beta2. This may be happended The Qt Foundation wrongly made a folder for 6.6.0 for beta2 then unhappily aqtinstall catch it.