Fix rubygems provider to use https instead of http.

### Version:
All

### Environment: 
Any that utilizes chef_gems from rubygems.org

### Scenario:
Installing any chef_gem results in a message from rubygems that http access is deprecated and should not be used.

### Steps to Reproduce:
Install a chef_gem and observe the provider output.

### Expected Result:
It should install with no warning from rubygems.

### Actual Result:
Rubygems states that http access is deprecated and all connections should use https.