VPC module in instances.tf conflicts with main.tf

[neoalienson]

vpc module in modules/instances/instances.tf:

https://github.com/quiccklabs/Labs_solutions/blob/master/Build%20Infrastructure%20with%20Terraform%20on%20Google%20Cloud%20Challenge%20Lab/quicklab345.sh#L461-L484

is duplicated and conflict with main.tf:

https://github.com/quiccklabs/Labs_solutions/blob/master/Build%20Infrastructure%20with%20Terraform%20on%20Google%20Cloud%20Challenge%20Lab/quicklab345.sh#L383-L406

[neoalienson]

Fix issue in #33