chore(vsce): remove unused @vscode/test-* devDependencies (#5252)

Phase 4.3 (#5250) replaced the old `vscode-test` script (which had no
.vscode-test.mjs config and could not run) with a Node test runner
(`npm run compile-tests && node --test "out/test/**/*.test.js"`), leaving
@vscode/test-cli and @vscode/test-electron unreferenced by any script or
source. Remove both devDependencies and regenerate package-lock.json,
which prunes the now-orphaned mocha-era subtree (cliui, jackspeak,
string-width, wrap-ansi, @isaacs/cliui, minimatch, ...).

Rebuilt on top of main after #5250 squash-merged; preserves main's later
devDependency bumps (@types/node, @typescript-eslint/parser, esbuild,
typescript-eslint) instead of reverting them.

compile (check-types + lint + esbuild) and the 26 unit tests stay green;
npm install reports 0 vulnerabilities.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: devantler