Remove unused "host" service

[robertknight]

As far as I can ascertain, this Angular service isn't used any more. There are no calls to its exported API (host.showSidebar, host.hideSidebar).

I'm currently checking whether there is any code in src/annotator that is also no longer used as a result.

[codecov-io]

Codecov Report

Merging #446 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #446      +/-   ##
==========================================
- Coverage   89.85%   89.82%   -0.03%     
==========================================
  Files         128      127       -1     
  Lines        5025     5014      -11     
  Branches      860      861       +1     
==========================================
- Hits         4515     4504      -11     
  Misses        510      510

Impacted Files	Coverage Δ
src/annotator/sidebar.coffee	81.25% <ø> (-0.39%)	⬇️
src/shared/polyfills.js	100% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7f96510...ab7f40d. Read the comment docs.

[robertknight]

I think I'm satisfied that the bridge events this code used to listen for are not emitted anywhere and the event listeners for the events that this module used to send to the host frame are no longer used either.

[seanh]

Good find