fix: don't call twice startSyncFilesTimeout method

[Fatme]

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the [CLA].
• All existing tests are passing: https://github.com/NativeScript/nativescript-dev-webpack/blob/master/CONTRIBUTING.md#testing-locally-by-running-e2e-tests
• Tests for the changes are included.

What is the current behavior?

startSyncFilesTimeout is called twice with next versions of {N} CLI and nativescript-dev-webpack plugin

What is the new behavior?

startSyncFilesTimeout is called only once with next versions of {N} CLI and nativescript-dev-webpack plugin

[SvetoslavTsenov]

Hey @Fatme, almost all checks has passed, except two failing jobs but they are red even on master so this should not stop you to merge the PR.