fix: don't create examples db on 'superset init'

[mistercrunch]

SUMMARY

superset init should not create the examples database as it does now

closes #9879

[codecov-commenter]

Codecov Report

Merging #9881 into master will decrease coverage by 0.14%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #9881      +/-   ##
==========================================
- Coverage   71.24%   71.10%   -0.15%     
==========================================
  Files         584      584              
  Lines       30790    30606     -184     
  Branches     3238     3142      -96     
==========================================
- Hits        21936    21761     -175     
+ Misses       8744     8736       -8     
+ Partials      110      109       -1     

Flag	Coverage Δ
#cypress	53.83% <ø> (ø)
#javascript	59.44% <ø> (ø)
#python	71.14% <83.33%> (-0.25%)	⬇️

Impacted Files	Coverage Δ
superset/cli.py	36.72% <ø> (-3.00%)	⬇️
superset/viz_sip38.py	0.00% <0.00%> (ø)
superset/db_engine_specs/base.py	87.20% <100.00%> (ø)
superset/errors.py	100.00% <100.00%> (ø)
superset/sql_parse.py	99.29% <100.00%> (-0.01%)	⬇️
superset/views/base.py	73.21% <100.00%> (-0.24%)	⬇️
superset/viz.py	71.85% <100.00%> (-0.12%)	⬇️
superset/views/tags.py	35.13% <0.00%> (-4.11%)	⬇️
superset/models/sql_types/presto_sql_types.py	72.41% <0.00%> (-4.06%)	⬇️
superset/models/tags.py	58.58% <0.00%> (-3.80%)	⬇️
... and 31 more

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[mistercrunch]

Looks like isort is having some confusion around py3.6 and py3.7 (?)

I'm 3.7 locally somehow, but CI is 3.6 and passes...