Fix GZipMiddleware example

[dbanty]

Fixes #1067

[codecov]

Codecov Report

Merging #1068 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1068   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          331       331           
  Lines         8085      8085           
=========================================
  Hits          8085      8085           

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[arimbr]

Feels like we were other two to open a PR:
#1138
#1146

PR #1138 also changes hl_lines to match the highlighted code lines for the new block.

[dbanty]

Yup, #1138 is better

[tiangolo]

Thanks everyone! 🍰