Fix mismatched command names in example strings

[beardicus]

Summary

Fixes several `example` strings that use incorrect command names, which prevents the docs site from parsing them correctly. The example field must use the exact command name matching the `name` field.

Changes

• `network attachment create` (partner_network_connect.go): Changed `doctl network connect create` → `doctl network attachment create`
• `network byoip-prefix resource` (byoip_prefix.go): Changed `doctl network byoip-prefix resources` → `doctl network byoip-prefix resource` (singular, matching the command name)
• `security scans create` (security.go): Changed `doctl security scan create` → `doctl security scans create`
• `security scans get` (security.go): Changed `doctl security scan get` → `doctl security scans get`
• `security scans list` (security.go): Changed `doctl security scan list` → `doctl security scans list`