Pin grpc version (#523)

* Pin grpc 1.73.0

Change-Id: I8791fc28de865fec160666c9120e6927fd926102

* Update CHANGELOG

Change-Id: I25fbcbd25e2002f515095e905442e707eeaa0cbf

* Add more detail

Change-Id: Iafa1d05b5503db7a72a463508d9c7ab0ba088b16

Author: dorasun

CHANGELOG.md

@@ -3,6 +3,7 @@
  - Compatibility with v21, v20.1, v19.2 of the API: https://developers.google.com/google-ads/api/docs/release-notes
  - Removed support for v18.
  - Updated examples to include the `containsEuPoliticalAdvertising` field on campaign creation.
+ - Pinned grpc version 1.73.0. See [issue#524](https://github.com/googleads/google-ads-ruby/issues/524) for background. This is a temporary workaround that will be removed in the future.
 
 34.2.0
 -----

Gemfile

@@ -15,3 +15,4 @@ gem 'benchmark-ips'
 gem 'yard'
 gem 'rubocop', require: false
 gem 'rubocop-google_ads', require: false
+gem 'grpc', '~> 1.73'