Make Embedded Video Iframe Responsive in Mobile View and avoid overflow

[sarthak-kumar-shailendra]

Fixes #8479
I have gone through almost all of the iframes in this repo and the fix can be seen on

1. https://www.jenkins.io/solutions/embedded/
2. https://www.jenkins.io/solutions/ruby/
3. https://www.jenkins.io/solutions/pipeline/
4. https://www.jenkins.io/projects/gsoc/2018/remoting-over-message-bus/.
5. https://www.jenkins.io/zh/blog/2015/12/02/hacksgiving-left-overs/
6. https://www.jenkins.io/blog/2011/10/17/andrew-bayer-discusses-jenkins-with-tim-obrien/
7. https://www.jenkins.io/blog/2019/10/21/thinking-about-jenkins-security/
8. https://www.jenkins.io/blog/2019/10/24/jenkins-performance-avoiding-pitfalls/
9. https://www.jenkins.io/blog/2011/04/04/the-final-two-run-off-vote-for-the-new-jenkins-logo/
10. https://www.jenkins.io/blog/2011/03/21/the-polls-are-open-for-the-jenkins-logo-contest/

The issue has now been resolved by applying a responsive styling fix directly in the main.css file, ensuring consistent iframe behavior across all devices and preventing similar issues in the future.
On the last five urls where the center tag was not used, I applied the necessary changes directly within the individual files.