Remove f1-micro from machine type dropdown when creating GKE cluster

Summary

Creation of GKE cluster using f1-micro fails, since it is officially unsupported according to https://cloud.google.com/kubernetes-engine/docs/concepts/cluster-architecture#memory_cpu

Note: f1-micro machines are not supported, because they do not have sufficient memory to run GKE.

Related issue: #23755 (closed)

Twitter: https://twitter.com/MolloyLaurence/status/1282033634032132097

Steps to reproduce

1. Create gitlab group
2. Try to add GKE cluster in any zone with f1-micro instances

What is the current bug behavior?

Creation of cluster fails

What is the expected correct behavior?

Basically, f1-micro option should not be available

Output of checks

This bug happens on GitLab.com