Bump the http client to apache http client 5

[ryantomli]

The custom http client used by sendgrid-java is out of date and there is an open issue and a PR (I raised) to update it, but it doesn't seem like that repo is monitored maybe.

If someone that tends to this repo could take a look that would be helpful!

Issue: sendgrid/java-http-client#147
PR: sendgrid/java-http-client#148

[sbarinov-pegbo]

Currently, the official spedgrid-java library is not compatible with spring 6.x. According to https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.0-Migration-Guide#apache-httpclient-in-resttemplate httpclient v4.x support is removed. So, we're not able to use sendgrid library in our project with the latest spring releases.
Please merge!