This script, examples/ruby/advanced_operations/add_responsive_search_ad_full.rb,
is the Ruby equivalent of the Python example
examples/advanced_operations/add_responsive_search_ad_full.py.

It demonstrates how to create a comprehensive Responsive Search Ad setup,
including:
- Optional ad customizer attributes and customer-level linking.
- Campaign budget creation.
- Campaign creation with paused status, search channel, target spend bidding
  strategy, and network settings.
- Ad group creation.
- Responsive Search Ad creation with pinned headlines, multiple descriptions
  (one potentially using ad customizers), and URL paths.
- Addition of keywords with exact, phrase, and broad match types.
- Geo-targeting for the campaign based on location names.

The script uses the `google-ads-googleads` gem, parses command-line
arguments for your customer ID and an optional customizer attribute name,
and includes error handling.

This commit refactors the `add_responsive_search_ad_full.rb` script to remove the `optimist` and `securerandom` dependencies.

- The `optimist` gem is replaced with Ruby's built-in `OptionParser` for command-line argument parsing.
- The `securerandom` gem is replaced with the `uuid` gem for generating UUIDs.
- All functionality related to ad customizers has been removed from the script to simplify its purpose.
- The `Gemfile` has been updated to reflect these dependency changes.