fix(vue-app): triggerScroll when transitions is disabled

[pimlie]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

On a normal page change nuxt relies on the routeEnter hook of the transition to emit a triggerScroll event to resolve the scrollBehaviour: https://github.com/nuxt/nuxt.js/blob/dev/packages/vue-app/template/App.js#L65

When you set features.transitions: false then this event is never emitted, so scrollBehaviour is broken. This pr fixes that by always emitting triggerScroll in fixPrepatch when you've set features.transitions = false

The proposed change should work fine as the minifier should be able to remove the constant condition that exists when transitions = false

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.