Bump tokio to 1.20.x

[kostko]

No description provided.

[codecov]

Codecov Report

Merging #4928 (91090a7) into master (10925b2) will decrease coverage by 0.03%.
The diff coverage is n/a.

❗ Current head 91090a7 differs from pull request most recent head c2c28b4. Consider uploading reports for the commit c2c28b4 to get more accurate results

@@            Coverage Diff             @@
##           master    #4928      +/-   ##
==========================================
- Coverage   66.71%   66.68%   -0.04%     
==========================================
  Files         464      464              
  Lines       51127    51127              
==========================================
- Hits        34110    34094      -16     
- Misses      12836    12848      +12     
- Partials     4181     4185       +4     

Impacted Files	Coverage Δ
...onsensus/tendermint/apps/beacon/state/state_vrf.go	73.33% <0.00%> (-13.34%)	⬇️
go/worker/keymanager/watcher.go	63.07% <0.00%> (-10.77%)	⬇️
go/runtime/host/sandbox/sandbox.go	71.33% <0.00%> (-6.49%)	⬇️
go/common/cbor/codec.go	78.37% <0.00%> (-5.41%)	⬇️
go/common/grpc/auth/auth.go	94.73% <0.00%> (-5.27%)	⬇️
go/worker/beacon/tx_retry.go	90.47% <0.00%> (-4.77%)	⬇️
go/storage/mkvs/lookup.go	75.00% <0.00%> (-4.17%)	⬇️
go/consensus/tendermint/apps/registry/query.go	80.00% <0.00%> (-4.00%)	⬇️
go/common/sgx/common.go	66.01% <0.00%> (-3.89%)	⬇️
go/sentry/api/grpc.go	40.62% <0.00%> (-3.13%)	⬇️
... and 19 more

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[pro-wh]

as described

[kostko]

The need to lock tokio to at most 1.20.x should be removed soon (tokio-rs/tokio#4999, tokio-rs/tokio#5000, tokio-rs/tokio#5001).