Fix colors in ellipsis

[betodealmeida]

CATEGORY

Choose one

• Bug Fix
• Enhancement (new features, refinement)
• Refactor
• Add tests
• Build / Development Environment
• Documentation

SUMMARY

For expanded columns in SQL Lab, the ellipsis had the wrong color.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before it was black, while the label was gray. Now:

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

REVIEWERS

@khtruong

[codecov-io]

Codecov Report

Merging #7632 into master will decrease coverage by 0.02%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master    #7632      +/-   ##
==========================================
- Coverage   65.59%   65.57%   -0.03%     
==========================================
  Files         435      435              
  Lines       21694    21745      +51     
  Branches     2387     2393       +6     
==========================================
+ Hits        14230    14259      +29     
- Misses       7343     7365      +22     
  Partials      121      121

Impacted Files	Coverage Δ
...src/components/FilterableTable/FilterableTable.jsx	90.21% <75%> (+1.08%)	⬆️
superset/security.py	73.12% <0%> (-1.88%)	⬇️
superset/assets/src/SqlLab/reducers/sqlLab.js	48.38% <0%> (-1.07%)	⬇️
.../assets/src/SqlLab/components/AceEditorWrapper.jsx	57.31% <0%> (-1.02%)	⬇️
.../assets/src/SqlLab/components/SqlEditorLeftBar.jsx	39.62% <0%> (-0.81%)	⬇️
superset/assets/src/SqlLab/actions/sqlLab.js	63.4% <0%> (-0.79%)	⬇️
superset/utils/core.py	88.06% <0%> (-0.18%)	⬇️
...uperset/assets/src/SqlLab/components/SqlEditor.jsx	54.03% <0%> (ø)	⬆️
...ets/src/visualizations/FilterBox/transformProps.js	0% <0%> (ø)	⬆️
superset/__init__.py	73.52% <0%> (ø)	⬆️
... and 6 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 15d0361...1f64a8f. Read the comment docs.

[mistercrunch]

LGTM, one minor thing from a previous PR, headerRenderer method should be renderHeader to align with the naming style in other components