placement: remove stale code

[disksing]

Signed-off-by: disksing i@disksing.com

What problem does this PR solve?

Remove some code based on staled design (never used).

Check List

Tests

• No code

[lhy1024]

What did they originally plan to be used for?

[codecov-io]

Codecov Report

Merging #1855 into master will decrease coverage by 0.13%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1855      +/-   ##
==========================================
- Coverage   77.97%   77.84%   -0.14%     
==========================================
  Files         168      166       -2     
  Lines       17034    16895     -139     
==========================================
- Hits        13283    13152     -131     
+ Misses       2664     2659       -5     
+ Partials     1087     1084       -3

Impacted Files	Coverage Δ
pkg/mock/mockcluster/mockcluster.go	90.2% <0%> (-1.75%)	⬇️
server/grpc_service.go	57.04% <0%> (-0.66%)	⬇️
client/client.go	68.6% <0%> (-0.44%)	⬇️
server/cluster.go	84.49% <0%> (-0.25%)	⬇️
server/schedule/operator/operator.go	85.53% <0%> (+0.35%)	⬆️
server/schedulers/shuffle_hot_region.go	61.79% <0%> (+5.61%)	⬆️

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[disksing]

@lhy1024 Same target. But design is not good.

[lhy1024]

LGTM

[sre-bot]

/run-all-tests