Remove "grid" role from keypad

[nedredmond]

LC-1356

Removes "grid" role from keypad. Its presence without "row" and "gridcell" roles in child elements muddles the screen reader experience.

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/lemon-bears-remain.md, packages/math-input/src/components/keypad/keypad.tsx, packages/math-input/src/components/keypad/__tests__/__snapshots__/keypad.test.tsx.snap

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[github-actions]

npm Snapshot: Published

🎉 Good news!! We've packaged up the latest commit from this PR (42ab4e8) and published it to npm. You
can install it using the tag PR760.

Example:

yarn add @khanacademy/perseus@PR760

[github-actions]

Size Change: -7 B (0%)

Total Size: 850 kB

Filename	Size	Change
packages/math-input/dist/es/index.js	104 kB	-7 B (0%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.1 kB
packages/kmath/dist/es/index.js	4.25 kB
packages/perseus-core/dist/es/index.js	934 B
packages/perseus-editor/dist/es/index.js	268 kB
packages/perseus-error/dist/es/index.js	846 B
packages/perseus-linter/dist/es/index.js	21.4 kB
packages/perseus/dist/es/index.js	396 kB
packages/pure-markdown/dist/es/index.js	3.77 kB
packages/simple-markdown/dist/es/index.js	12.3 kB

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[handeyeco]

Looks good, thank you!