Add deprecation warning filter

[ahopkins]

closes #2538

app.config.DEPRECATION_FILTER = "ignore"

Allowed values

[codecov]

Codecov Report

Base: 87.846% // Head: 87.834% // Decreases project coverage by -0.012% ⚠️

Coverage data is based on head (1d695ad) compared to base (4726cf1).
Patch coverage: 83.333% of modified lines in pull request are covered.

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #2546       +/-   ##
=============================================
- Coverage   87.846%   87.834%   -0.013%     
=============================================
  Files           78        78               
  Lines         6451      6461       +10     
  Branches      1244      1246        +2     
=============================================
+ Hits          5667      5675        +8     
- Misses         559       560        +1     
- Partials       225       226        +1     

Impacted Files	Coverage Δ
sanic/app.py	87.500% <ø> (-0.044%)	⬇️
sanic/config.py	97.452% <83.333%> (-1.169%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[sjsadowski]

LGTM.