wdio-cli: fix typo (#3828)

## Proposed changes

Replace log string `tests` by `test suites` on stdout.

## Types of changes

- [x] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

## Checklist

- [x] I have read the [CONTRIBUTING](https://github.com/webdriverio/webdriverio/blob/master/CONTRIBUTING.md) doc
- [ ] I have added tests that prove my fix is effective or that my feature works
- [ ] I have added necessary documentation (if appropriate)

### Reviewers: @webdriverio/technical-committee

packages/wdio-cli/src/interface.js

@@ -236,10 +236,10 @@ export default class WDIOCLInterface extends EventEmitter {
             if (runningJobs > MAX_RUNNING_JOBS_DISPLAY_COUNT) {
                 logString.push(
                     runningJobs - MAX_RUNNING_JOBS_DISPLAY_COUNT,
-                    'running tests' + (pendingJobs ? ' -' : ''))
+                    'running test suites' + (pendingJobs ? ' -' : ''))
             }
             if (pendingJobs) {
-                logString.push(pendingJobs, 'pending tests')
+                logString.push(pendingJobs, 'pending test suites')
             }
             this.display.push(chalk.yellow('...', ...logString.filter(l => Boolean(l))))
         }