fix: shadow global Symbol in async-iterator to resolve lint

The CI JavaScript lint job on develop has been failing since 2026-05-01:

  symbol/async-iterator/lib/main.js 42:65
  error  The 'Symbol.asyncIterator' is still an experimental feature
  and is not supported until Node.js 10.0.0.
  (n/no-unsupported-features/es-builtins)

Root cause: the file references the global `Symbol.asyncIterator`
directly. The `n/no-unsupported-features/es-builtins` rule flags any
global `Symbol.*` access when the configured engine range
(`>=0.12.18`) predates Node.js 10. Adding a local
`var Symbol = require( '@stdlib/symbol/ctor' )` shadows the global,
resolving the rule without altering runtime behavior (the
`hasAsyncIteratorSymbolSupport()` guard already short-circuits the
ternary on environments where the local Symbol would be undefined).

This pattern is identical to `@stdlib/symbol/to-primitive` (line 24).

Failing run: https://github.com/stdlib-js/stdlib/actions/runs/25195861572

Author: Planeshifter

lib/node_modules/@stdlib/symbol/async-iterator/lib/main.js

@@ -21,6 +21,7 @@
 // MODULES //
 
 var hasAsyncIteratorSymbolSupport = require( '@stdlib/assert/has-async-iterator-symbol-support' ); // eslint-disable-line id-length
+var Symbol = require( '@stdlib/symbol/ctor' );
 
 
 // MAIN //