fix: KVSearchDriver is_merge should be False by default

[cristianmtr]

This is to prevent duplicating the embedding and raising the reshaping error in Document (ValueError: cannot reshape array of size 10 into shape (10,10))

A more robust solution should be discussed in the future

[codecov]

Codecov Report

Merging #1701 (b2275ba) into master (321a890) will increase coverage by 0.23%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #1701      +/-   ##
==========================================
+ Coverage   84.82%   85.06%   +0.23%     
==========================================
  Files         133      133              
  Lines        6848     6856       +8     
==========================================
+ Hits         5809     5832      +23     
+ Misses       1039     1024      -15     

Impacted Files	Coverage Δ
jina/flow/base.py	87.12% <33.33%> (-0.45%)	⬇️
jina/peapods/runtimes/jinad/__init__.py	94.11% <33.33%> (-5.89%)	⬇️
jina/drivers/search.py	96.49% <100.00%> (ø)
jina/flow/builder.py	73.91% <100.00%> (+0.57%)	⬆️
jina/peapods/runtimes/jinad/api.py	86.84% <100.00%> (+11.18%)	⬆️
jina/peapods/runtimes/asyncio/rest/app.py	91.17% <0.00%> (+1.96%)	⬆️

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[github-actions]

Latency summary

Current PR yields:

• 😶 index QPS at 1641, delta to last 3 avg.: -1%
• 😶 query QPS at 32, delta to last 3 avg.: -2%

Breakdown

Version	Index QPS	Query QPS
current	1641	32
0.9.13	1663	32
0.9.12	1658	33

Backed by latency-tracking. Further commits will update this comment.

[cristianmtr]

Fixed a test