Upgrade syntax to 3.11

[hippalectryon-0]

Follow-up of #427

[Draft until #427 is merged]

Steps

• Run find qubesadmin -name '*.py' -exec uvx -p 3.11 pyupgrade --py311-plus {} +

[codecov]

Codecov Report

❌ Patch coverage is 65.71429% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.04%. Comparing base (8ebd096) to head (fd23fb2).

Files with missing lines	Patch %	Lines
qubesadmin/backup/restore.py	30.00%	7 Missing ⚠️
qubesadmin/tools/__init__.py	44.44%	5 Missing ⚠️
qubesadmin/tools/dochelpers.py	0.00%	5 Missing ⚠️
qubesadmin/tools/qvm_backup.py	0.00%	4 Missing ⚠️
qubesadmin/tools/qvm_start_daemon.py	42.85%	4 Missing ⚠️
qubesadmin/tools/qvm_pool_legacy.py	0.00%	3 Missing ⚠️
qubesadmin/backup/core3.py	0.00%	2 Missing ⚠️
qubesadmin/tools/qvm_create.py	0.00%	2 Missing ⚠️
qubesadmin/tools/qvm_ls.py	66.66%	2 Missing ⚠️
qubesadmin/tools/qvm_run.py	50.00%	2 Missing ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #428      +/-   ##
==========================================
- Coverage   76.07%   76.04%   -0.03%     
==========================================
  Files          53       53              
  Lines        9286     9277       -9     
==========================================
- Hits         7064     7055       -9     
  Misses       2222     2222              

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