Remove 'src' directory from package files in abilities package

[kushagra-goyal-14]

What?

Part of #77274

Removes src from the files field in @wordpress/abilities's package.json.

Why?

The package defines an exports field that only exposes built artifacts (build/, build-module/, build-types/). Per Node.js module resolution, consumers cannot access files outside of exports. Shipping the src/ directory is unnecessary and inflates the published package size.

How?

Removes "src" from the files array.

Testing Instructions

1. Verify the package builds: npm run build
2. Verify npm pack --dry-run in packages/abilites/ no longer includes src/

Screenshots

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