[Interactive Graph: Circle] Add a key prop to the circle drag handle

[nishasy]

Summary:

There's always a console error saying that the circle graph drag handle
is missing the key prop.

Adding a key here.

Issue: none

Test plan:

Open the console and make sure the error isn't showing up anymore.

yarn jest packages/perseus/src/widgets/__tests__/interactive-graph.test.ts
Make sure the logs don't show the console error anymore.

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/sour-cougars-draw.md, packages/perseus/src/widgets/interactive-graphs/graphs/circle.tsx

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[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (048a47b) and published it to npm. You
can install it using the tag PR1388.

Example:

yarn add @khanacademy/perseus@PR1388

If you are working in Khan Academy's webapp, you can run:

./dev/tools/bump_perseus_version.sh -t PR1388

[benchristel]

Oh, this is because the six dots in the drag handle are generated from coordinates. Thanks for the fix!

[github-actions]

Size Change: +24 B (0%)

Total Size: 849 kB

Filename	Size	Change
packages/perseus/dist/es/index.js	410 kB	+24 B (+0.01%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.2 kB
packages/kmath/dist/es/index.js	4.26 kB
packages/math-input/dist/es/index.js	80.1 kB
packages/math-input/dist/es/strings.js	1.73 kB
packages/perseus-core/dist/es/index.js	906 B
packages/perseus-editor/dist/es/index.js	272 kB
packages/perseus-error/dist/es/index.js	866 B
packages/perseus-linter/dist/es/index.js	21.8 kB
packages/perseus/dist/es/strings.js	3.21 kB
packages/pure-markdown/dist/es/index.js	3.67 kB
packages/simple-markdown/dist/es/index.js	12.4 kB

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.85%. Comparing base (30f898c) to head (048a47b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1388      +/-   ##
==========================================
+ Coverage   69.79%   70.85%   +1.06%     
==========================================
  Files         493      497       +4     
  Lines      104304   104388      +84     
  Branches     5293    11276    +5983     
==========================================
+ Hits        72794    73962    +1168     
+ Misses      31394    30426     -968     
+ Partials      116        0     -116     

Files	Coverage Δ
...s/src/widgets/interactive-graphs/graphs/circle.tsx	98.46% <100.00%> (+0.01%)	⬆️

... and 127 files with indirect coverage changes

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