fix: Chart download as image issue

[codemaster08240328]

SUMMARY

This pr resolves the issue which is about downloading chart as image.

Why this issue happened:

We were passing wrong query selector for chart element to downloadAsImage() function, which returned undefined from document.querySelector().

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

1. Goto chart explore page
2. Select any chart
3. Try to download chart as image from 3 dots button on top right corner.

Expected result:
Should be able to see the downloaded image of chart.

ADDITIONAL INFORMATION

• Fix Issue.

[diegomedina248]

Can we add a test for this? Maybe a cypress one?

[yousoph]

/testenv up

[github-actions]

@yousoph Ephemeral environment spinning up at http://54.200.13.34:8080. Credentials are admin/admin. Please allow several minutes for bootstrapping and startup.

[codecov]

Codecov Report

Merging #19885 (a7b086a) into master (ae38411) will decrease coverage by 0.03%.
The diff coverage is 52.24%.

❗ Current head a7b086a differs from pull request most recent head 0b0868c. Consider uploading reports for the commit 0b0868c to get more accurate results

@@            Coverage Diff             @@
##           master   #19885      +/-   ##
==========================================
- Coverage   66.55%   66.52%   -0.04%     
==========================================
  Files        1692     1714      +22     
  Lines       64802    65032     +230     
  Branches     6657     6717      +60     
==========================================
+ Hits        43129    43260     +131     
- Misses      19973    20065      +92     
- Partials     1700     1707       +7     

Flag	Coverage Δ
javascript	51.25% <46.97%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
...-chart-controls/src/sections/advancedAnalytics.tsx	14.28% <0.00%> (-19.05%)	⬇️
...d/packages/superset-ui-chart-controls/src/types.ts	100.00% <ø> (ø)
...preset-chart-deckgl/src/layers/Geojson/Geojson.jsx	0.00% <0.00%> (ø)
...et-chart-deckgl/src/layers/Geojson/controlPanel.ts	50.00% <ø> (ø)
...hart-echarts/src/MixedTimeseries/transformProps.ts	0.00% <ø> (ø)
...gin-chart-echarts/src/Timeseries/transformProps.ts	57.89% <ø> (ø)
...plugins/plugin-chart-handlebars/src/Handlebars.tsx	0.00% <0.00%> (ø)
...ars/src/components/Handlebars/HandlebarsViewer.tsx	0.00% <0.00%> (ø)
...frontend/plugins/plugin-chart-table/src/Styles.tsx	100.00% <ø> (ø)
...frontend/src/SqlLab/components/SqlEditor/index.jsx	51.07% <0.00%> (-0.28%)	⬇️
... and 54 more

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[yousoph]

Quick testing on the ephemeral env looks good

[github-actions]

Ephemeral environment shutdown and build artifacts deleted.

[rusackas]

@codemaster08240328 will be adding tests later in a separate PR.

[sadpandajoe]

🏷️ preset:2022.17