src: remove AbortSignal import

AbortSignal is available in all supported versions of Node. These
imports were causing problems when attempting to upgrade TypeScript
settings because apparently 'node-fetch/externals' exists in the
types package, but not in the actual node-fetch module.

src/log.ts

@@ -1,5 +1,4 @@
 import fetch from 'node-fetch';
-import { AbortSignal } from 'node-fetch/externals';
 import { Writable } from 'node:stream';
 import { ApiException } from './api';
 import { KubeConfig } from './config';

src/watch.ts

@@ -1,6 +1,5 @@
 import { createInterface } from 'node:readline';
 import fetch from 'node-fetch';
-import { AbortSignal } from 'node-fetch/externals';
 import { KubeConfig } from './config';
 
 export class Watch {