[test] fix URL for restrooms_spec

[dunn]

Without the leading slash:

  1) Restrooms API queries filters a list of restrooms by updated date finds all restrooms
     Failure/Error: get "api/v1/restrooms/by_date", updated: true,  day: Date.today.day, month: Date.today.month, year: Date.today.year
     URI::InvalidURIError:
       bad URI(is not URI?): http://www.example.com:80api/v1/restrooms/by_date
     # ./spec/api/v1/restrooms_spec.rb:181:in `block (4 levels) in <top (required)>'

  2) Restrooms API queries filters a list of restrooms by updated date is successful
     Failure/Error: get "api/v1/restrooms/by_date", updated: true,  day: Date.today.day, month: Date.today.month, year: Date.today.year
     URI::InvalidURIError:
       bad URI(is not URI?): http://www.example.com:80api/v1/restrooms/by_date
     # ./spec/api/v1/restrooms_spec.rb:181:in `block (4 levels) in <top (required)>'

[tkwidmer]

Looks good!