ci(rollup): disable npm caching to fix build error

Build error:

```
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR!
npm ERR! Found: @rollup/plugin-typescript@2.1.0
npm ERR! node_modules/@rollup/plugin-typescript
npm ERR!   dev @rollup/plugin-typescript@"^6.1.0" from the root project
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! dev @rollup/plugin-typescript@"^6.1.0" from the root project
npm ERR!
npm ERR! Conflicting peer dependency: rollup@2.33.1
npm ERR! node_modules/rollup
npm ERR!   peer rollup@"^2.14.0" from @rollup/plugin-typescript@6.1.0
npm ERR!   node_modules/@rollup/plugin-typescript
npm ERR!     dev @rollup/plugin-typescript@"^6.1.0" from the root project
```

https://docs.travis-ci.com/user/languages/javascript-with-nodejs/#caching-with-npm

.travis.yml

@@ -1,6 +1,8 @@
 language: node_js
 node_js:
   - stable
+cache:
+  npm: false
 install:
   - npm install
 script: