chore: Updating SIP issue template to boost the link, and (hopefully) reduce duplicate-numbered SIP issues.

[rusackas]

SUMMARY

This PR does a few things:

1. Moves the link to SIP-0 to the template list page (not sure if this will work!)
2. Removes instructions for people to number their own sip. A committer should do this, per SIP-0
3. Adjusts the PR title accordingly to item 2.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A

TESTING INSTRUCTIONS

Open a new issue when merged, make sure the link works!

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #21896 (bc081e2) into master (52d33b0) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #21896      +/-   ##
==========================================
+ Coverage   66.90%   66.91%   +0.01%     
==========================================
  Files        1805     1805              
  Lines       69073    69064       -9     
  Branches     7369     7369              
==========================================
+ Hits        46214    46217       +3     
+ Misses      20952    20933      -19     
- Partials     1907     1914       +7     

Flag	Coverage Δ
hive	52.92% <ø> (ø)
javascript	53.31% <ø> (+0.02%)	⬆️
mysql	78.35% <ø> (ø)
postgres	78.41% <ø> (ø)
presto	52.82% <ø> (ø)
python	81.47% <ø> (ø)
sqlite	76.90% <ø> (ø)
unit	51.06% <ø> (ø)

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

Impacted Files	Coverage Δ
...et-frontend/src/dashboard/actions/dashboardInfo.ts	50.00% <0.00%> (-11.54%)	⬇️
.../src/dashboard/components/gridComponents/Chart.jsx	53.57% <0.00%> (-1.48%)	⬇️
...-frontend/src/dashboard/reducers/dashboardState.js	76.08% <0.00%> (-0.51%)	⬇️
...frontend/src/dashboard/components/Header/index.jsx	59.85% <0.00%> (-0.45%)	⬇️
...rontend/src/dashboard/containers/DashboardPage.tsx	7.14% <0.00%> (-0.12%)	⬇️
superset-frontend/src/explore/ExplorePage.tsx	0.00% <0.00%> (ø)
...ntend/packages/superset-ui-core/src/color/index.ts	100.00% <0.00%> (ø)
...ntend/src/dashboard/containers/DashboardHeader.jsx	66.66% <0.00%> (ø)
...nd/src/dashboard/containers/DashboardComponent.jsx	85.00% <0.00%> (ø)
...uperset-ui-core/src/color/CategoricalColorScale.ts	100.00% <0.00%> (ø)
... and 6 more

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[betodealmeida]

Should we do this through a SIP? #meta

[geido]

LGTM! On a side note, I have been re-running some failing Cypress tests for this PR. We should probably dedicate some time to fix as many flaky tests as possible. Most of the failing tests appear on CI not locally. It requires a bit of investigation work.