Mails are not being sent after updating sparkpost's dependencies

Problem/Motivation

Emails are not being send in the project after updating sparkpost dependencies. This happens because when the sparkpost dependencies are updated, the package php-http/message, which is required by sparkpost/sparkpost, is updated to the 1.16.0 version which does not require php-http/message-factory anymore. More information: https://github.com/SparkPost/php-sparkpost/pull/211

This is a problem that must be solved at the sparkpost/sparkpost, but I report it here as I think some more projects may have the same issue.

Proposed resolution

Meanwhile the PR → is not merged and a release is done, the module description may indicate that projects must require php-http/message-factory so that sparkpost mails are sent.