raft: add chain core to notable users list

[tessr]

Per @xiang90's comment on #7515 (comment), this adds Chain Core to the notable users list for the raft package.

[xiang90]

lgtm. thanks @tessr

[heyitsanthony]

s/add chain core/raft: add chain core/ in the commit title so CI passes and this should be good to merge. Thanks!

[tessr]

eek, looks like it got merged anyways. Sorry about that--and thanks y'all

[codecov-io]

Codecov Report

Merging #7855 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #7855      +/-   ##
==========================================
- Coverage      76%   75.99%   -0.02%     
==========================================
  Files         332      332              
  Lines       26183    26183              
==========================================
- Hits        19901    19898       -3     
- Misses       4857     4862       +5     
+ Partials     1425     1423       -2

Impacted Files	Coverage Δ
clientv3/namespace/watch.go	87.87% <0%> (-12.13%)	⬇️
proxy/grpcproxy/watcher.go	85.41% <0%> (-8.34%)	⬇️
etcdserver/api/v3rpc/util.go	52.77% <0%> (-5.56%)	⬇️
proxy/grpcproxy/watch.go	89.58% <0%> (-4.87%)	⬇️
clientv3/concurrency/election.go	80% <0%> (-2.41%)	⬇️
integration/bridge.go	90.52% <0%> (-2.11%)	⬇️
etcdmain/etcd.go	44.2% <0%> (-1.29%)	⬇️
rafthttp/transport.go	81.92% <0%> (-1.13%)	⬇️
pkg/adt/interval_tree.go	87.19% <0%> (-0.61%)	⬇️
rafthttp/peer.go	91.6% <0%> (ø)	⬆️
... and 8 more

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