[dbnode] Remove unused Shard.ScanData method

[linasm]

What this PR does / why we need it:
Removed some dead code.

Special notes for your reviewer:

Does this PR introduce a user-facing and/or backwards incompatible change?:

Does this PR require updating code package or user-facing documentation?:

[codecov]

Codecov Report

Merging #3148 (9e14797) into master (7f1ce15) will decrease coverage by 0.0%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #3148     +/-   ##
=========================================
- Coverage    72.3%    72.2%   -0.1%     
=========================================
  Files        1084     1084             
  Lines      100288   100246     -42     
=========================================
- Hits        72519    72467     -52     
- Misses      22723    22736     +13     
+ Partials     5046     5043      -3     

Flag	Coverage Δ
aggregator	75.8% <ø> (-0.1%)	⬇️
cluster	84.8% <ø> (ø)
collector	84.3% <ø> (ø)
dbnode	78.7% <ø> (-0.1%)	⬇️
m3em	74.4% <ø> (ø)
m3ninx	73.1% <ø> (ø)
metrics	20.0% <ø> (ø)
msg	74.2% <ø> (+0.1%)	⬆️
query	67.2% <ø> (ø)
x	80.3% <ø> (-0.3%)	⬇️

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