chore(lint): drop the unused react eslint plugins

[frantuma]

Removes two ESLint plugins that were imported but never used. Small on its own, and it is what unblocks the eslint 10 upgrade that the open deps-dev PR (#4) cannot currently install.

They were dead

eslint.config.js imported both plugins at the top and never referenced either again:

import eslintPluginReact from 'eslint-plugin-react';
import eslintPluginJsxA11y from 'eslint-plugin-jsx-a11y';

Neither identifier appears anywhere else in the file, no react/ or jsx-a11y/ rule is configured in any config block, and the repository contains zero .tsx/.jsx files. They cost 37 packages in the tree and 569 lines of lockfile.

They block eslint 10

Both cap their eslint peer range at 9, which is the ERESOLVE that makes every installing job on #4 fail:

peer eslint@"^3 || ^4 || ^5 || ^6 || ^7 || ^8 || ^9" from eslint-plugin-jsx-a11y@6.10.2

Everything we keep already accepts eslint 10 — typescript-eslint and eslint-plugin-import-x are both ^8.57.0 || ^9.0.0 || ^10.0.0, @eslint/js@10 is ^10.0.0, eslint-config-prettier is >=7, eslint-plugin-prettier is >=8. eslint-plugin-mocha@12 goes further and requires eslint >=10.2.0, so mocha 12 and eslint 10 have to move together.

Verification

A/B dry run on this branch, which resolves the full tree without writing anything:

command	result
npm i --dry-run --no-save eslint@^10.10.0 @eslint/js@^10.0.1 eslint-plugin-mocha@^12.0.2	exit 0, resolves
the same plus eslint-plugin-jsx-a11y@^6.10.2	exit 1, ERESOLVE

That isolates the two removed plugins as the sole blocker rather than inferring it from the CI log.

Lint output is unchanged — 14 problems, 0 errors, 14 warnings, the same findings as main, all @typescript-eslint/no-explicit-any. That is the expected result for removing plugins that were never registered in any config block: had they been contributing rules, the count would move.

No behaviour change, no rule configuration touched. The actual eslint 10 bump follows in a separate PR.