[Lens] Validation errors are not vertically centered

[dej611]

Kibana version: master at 7503fd2

Describe the bug:

In Lens editor validation errors used to be centered aligned vertically.

Steps to reproduce:

1. Create a XY Chart in Lens
2. Add a new layer and add it only a dimension on the horizontal axis
3. Error being displayed

Expected behavior:

The message should be aligned as in previous versions.

Screenshots (if relevant):

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)