chore: Fix indentation issue

[john-bodley]

SUMMARY

Fixing an indentation issue (I suspect pylint would find this is configured correctly) whilst reading through the code. The extra_filters variable is not defined in the parent scope.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

CI.

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[codecov-commenter]

Codecov Report

Merging #10690 into master will decrease coverage by 4.85%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #10690      +/-   ##
==========================================
- Coverage   64.37%   59.51%   -4.86%     
==========================================
  Files         785      360     -425     
  Lines       36987    23184   -13803     
  Branches     3530        0    -3530     
==========================================
- Hits        23810    13799   -10011     
+ Misses      13068     9385    -3683     
+ Partials      109        0     -109     

Flag	Coverage Δ
#cypress	?
#javascript	?
#python	59.51% <100.00%> (-0.31%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
superset/tasks/cache.py	73.91% <100.00%> (ø)
superset/db_engine_specs/mysql.py	79.16% <0.00%> (-12.50%)	⬇️
superset/db_engine_specs/presto.py	70.91% <0.00%> (-11.41%)	⬇️
superset/examples/world_bank.py	97.10% <0.00%> (-2.90%)	⬇️
superset/examples/birth_names.py	97.36% <0.00%> (-2.64%)	⬇️
superset/views/database/mixins.py	80.70% <0.00%> (-1.76%)	⬇️
superset/models/core.py	86.38% <0.00%> (-1.12%)	⬇️
superset/connectors/sqla/models.py	89.45% <0.00%> (-0.28%)	⬇️
superset/views/core.py	74.26% <0.00%> (-0.25%)	⬇️
...-frontend/src/dashboard/containers/FilterScope.jsx
... and 424 more

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[nytai]

lgtm, @dpgaspar found something similar in https://github.com/apache/incubator-superset/pull/10576/files