apply pyupgrade --py39-plus

[CagtayFabry]

Changes

• update syntax to Python 3.9
• add pyupgrade precommit hook

Checks

• updated CHANGELOG.md

[github-actions]

Test Results

2 188 tests  ±0   2 187 ✔️ ±0   3m 11s ⏱️ +27s
       1 suites ±0          1 💤 ±0 
       1 files   ±0          0 ❌ ±0 

Results for commit e8f4b09. ± Comparison against base commit 3bef3e0.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

Merging #893 (e8f4b09) into master (3bef3e0) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #893      +/-   ##
==========================================
- Coverage   96.47%   96.46%   -0.01%     
==========================================
  Files          95       95              
  Lines        6292     6287       -5     
==========================================
- Hits         6070     6065       -5     
  Misses        222      222              

Files Changed	Coverage Δ
weldx/asdf/cli/welding_schema.py	97.00% <ø> (-0.03%)	⬇️
weldx/core/spatial_series.py	100.00% <ø> (ø)
weldx/asdf/file.py	96.30% <100.00%> (ø)
weldx/asdf/types.py	92.42% <100.00%> (-0.12%)	⬇️
weldx/asdf/util.py	90.28% <100.00%> (ø)
weldx/asdf/validators.py	98.24% <100.00%> (ø)
weldx/config.py	90.54% <100.00%> (-0.13%)	⬇️
weldx/core/generic_series.py	89.73% <100.00%> (ø)
weldx/core/math_expression.py	98.59% <100.00%> (ø)
weldx/core/time_series.py	97.74% <100.00%> (ø)
... and 12 more