Bump rust-toolchain to nightly-2021-05-06

[bohutang]

Summary

Bump rust-toolchain to nightly-2021-05-06

Changelog

• Build/Testing/CI

Related Issues

Fixes #575

Test Plan

Unit Tests
Stateless Tests

[bohutang]

The self runner is hang, I will reboot it later

[codecov-commenter]

Codecov Report

Merging #576 (50144dc) into master (65590e8) will increase coverage by 2%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #576    +/-   ##
=======================================
+ Coverage      79%     82%    +2%     
=======================================
  Files         294     291     -3     
  Lines       13844   13645   -199     
=======================================
+ Hits        11062   11227   +165     
+ Misses       2782    2418   -364     

Impacted Files	Coverage Δ
fusequery/query/src/sql/plan_parser_test.rs	96% <ø> (ø)
...pelines/transforms/transform_aggregator_partial.rs	84% <0%> (-2%)	⬇️
fusequery/query/src/configs/config.rs	97% <0%> (-2%)	⬇️
common/datavalues/src/data_value.rs	30% <0%> (-1%)	⬇️
common/planners/src/plan_rewriter.rs	85% <0%> (-1%)	⬇️
...uild/fuse-store-d1dedf7d0e8270dd/out/store_meta.rs
...common-flights-2401c197e1e2fc3f/out/queryflight.rs
...common-flights-2401c197e1e2fc3f/out/storeflight.rs
fusestore/store/src/dfs/distributed_fs_test.rs	95% <0%> (+<1%)	⬆️
fusequery/query/src/datasources/common_test.rs	97% <0%> (+<1%)	⬆️
... and 65 more

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