routing/http: fix goroutine/memory leak [skip changelog]

[MichaelMure]

I've noticed some memory and goroutine buildup, linked to that function.

It seems like when the context get cancelled, the consumer could be gone, but that function would still attempt to write in the channel and block forever.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 60.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 59.67%. Comparing base (625ba76) to head (b8219a9).

@@            Coverage Diff             @@
##             main     #618      +/-   ##
==========================================
- Coverage   59.80%   59.67%   -0.13%     
==========================================
  Files         239      239              
  Lines       29961    29961              
==========================================
- Hits        17917    17880      -37     
- Misses      10427    10458      +31     
- Partials     1617     1623       +6     

Files	Coverage Δ
routing/http/contentrouter/contentrouter.go	46.82% <60.00%> (-2.32%)	:arrow_down:

... and 16 files with indirect coverage changes