LIMS-742: Remove redundant 'pid' check

[ndg63276]

JIRA ticket: LIMS-742

Summary:

Since #566, there has been code left in to check if $pid was being sent to the api/users/ endpoint. As it doesn't seem to be, we can remove that logging, and also remove the $pid variable.

Changes:

• Remove $pid and logging of $pid

To test:

• Go to the home page, hover over the users icon for a visit, check a list of users appears
• Go to a visit, hover over the Users icon at the top, check a list of users appears
• Go to /projects, and create a new project. Add a user to the project by searching, and check they remain after refreshing the page
• Go to /contacts and click Add Home Lab Contact. Check your name appears in the dropdown labelled Login.
• Go to a shipment and click to add a container. Check a list of people appears in the dropdown labelled Owner.