ref: kill unused to_unicode and pprint template filter

[asottile-sentry]

leftovers from python 2

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.90%. Comparing base (5849309) to head (9d9c1a1).

❗ Current head 9d9c1a1 differs from pull request most recent head 511797f

Please upload reports for the commit 511797f to get more accurate results.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #71062       +/-   ##
===========================================
+ Coverage   51.07%   77.90%   +26.82%     
===========================================
  Files        6490     6520       +30     
  Lines      289340   290483     +1143     
  Branches    50072    50263      +191     
===========================================
+ Hits       147793   226288    +78495     
+ Misses     140050    57951    -82099     
- Partials     1497     6244     +4747     

Files	Coverage Δ
src/sentry/interfaces/http.py	53.84% <ø> (ø)
src/sentry/templatetags/sentry_helpers.py	69.37% <100.00%> (+30.77%)	⬆️
src/sentry/utils/strings.py	92.94% <100.00%> (+56.48%)	⬆️

... and 2112 files with indirect coverage changes