revendor cortex to latest master

[sandeepsukhani]

What this PR does / why we need it:
Updates cortex to latest master. This is just to get the latest query-tee changes from Cortex.

[codecov-commenter]

Codecov Report

Merging #2543 into master will increase coverage by 0.10%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master    #2543      +/-   ##
==========================================
+ Coverage   63.54%   63.65%   +0.10%     
==========================================
  Files         163      163              
  Lines       14325    14325              
==========================================
+ Hits         9103     9118      +15     
+ Misses       4507     4489      -18     
- Partials      715      718       +3     

Impacted Files	Coverage Δ
cmd/querytee/main.go	0.00% <0.00%> (ø)
pkg/logcli/query/query.go	38.65% <0.00%> (ø)
cmd/querytee/response_comparator.go	89.18% <100.00%> (ø)
pkg/logql/evaluator.go	92.47% <0.00%> (-0.41%)	⬇️
pkg/querier/queryrange/downstreamer.go	97.93% <0.00%> (+2.06%)	⬆️
pkg/promtail/positions/positions.go	59.64% <0.00%> (+13.15%)	⬆️

[slim-bean]

LGTM