fix(plugin-chart-echarts): fix Timeseries tooltip title

[maloun96]

Add format tooltip title as x axis

Close: apache/superset#13019

BEFORE

AFTER

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/superset/superset-ui/gv7vnlfsr
✅ Preview: https://superset-ui-git-fork-maloun96-timeseries-title-tooltip-2.superset.vercel.app

[codecov]

Codecov Report

Merging #956 (c5859b7) into master (59283de) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master     #956   +/-   ##
=======================================
  Coverage   27.68%   27.68%           
=======================================
  Files         401      401           
  Lines        8250     8250           
  Branches     1139     1139           
=======================================
  Hits         2284     2284           
  Misses       5830     5830           
  Partials      136      136           

Impacted Files	Coverage Δ
...gin-chart-echarts/src/Timeseries/transformProps.ts	45.83% <0.00%> (ø)

---

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 59283de...c5859b7. Read the comment docs.

[villebro]

Ah wonderful, I was annoyed by this just yesterday 👍