RN/Metro: Set reactRuntimeTarget on Hermes Parser (#50339)

Summary:
Pull Request resolved: #50339

Explicitly sets the default `reactRuntimeTarget` when invoking `require('hermes-parser').parse` so that it'll be easier to find these configurations when upgrading to `'19'`.

Changelog:
[Internal]

Reviewed By: javache

Differential Revision: D72006705

fbshipit-source-id: 4994917152a2a4a767b871d4a36092c0c5391324

Author: yungsters

Diff for: packages/react-native-codegen/src/parsers/flow/parseFlowAndThrowErrors.js

@@ -25,6 +25,7 @@ function parseFlowAndThrowErrors(
       babel: false,
       // Parse Flow without a pragma
       flow: 'all',
+      reactRuntimeTarget: '18',
       ...(options.filename != null ? {sourceFilename: options.filename} : {}),
     });
   } catch (e) {