deprecation: deprecate the use of remove_route

[yunstanford]

#1511 for 19.06

[codecov]

Codecov Report

Merging #1568 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1568      +/-   ##
==========================================
+ Coverage   91.35%   91.35%   +<.01%     
==========================================
  Files          18       18              
  Lines        1827     1828       +1     
  Branches      351      351              
==========================================
+ Hits         1669     1670       +1     
  Misses        132      132              
  Partials       26       26

Impacted Files	Coverage Δ
sanic/app.py	92.48% <100%> (+0.01%)	⬆️

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[ahopkins]

For reference... https://community.sanicframework.org/t/removing-routes-necessary-functionality/29?u=ahopkins