Replaces loom iframes with wistia inline iframes

[ZPain8464]

This PR adds the inline iframes from Wistia for the Routing, Policies, and Custom Domains videos. @nhayfield I had to manually add the iframe parameter to the URL. It seems to work, but I wanted to get your eyes on it to make sure in case I missed something.

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[nhayfield]

Code looks good.

[backport-actions-token]

The backport to 0-26-0 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-0-26-0 0-26-0
# Navigate to the new working tree
cd .worktrees/backport-0-26-0
# Create a new branch
git switch --create backport-1443-to-0-26-0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick --mainline 1 78bf5e5ca7d595714ce0f3cca4dc120b5b96ca8c
# Push it to GitHub
git push --set-upstream origin backport-1443-to-0-26-0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-0-26-0

Then, create a pull request where the base branch is 0-26-0 and the compare/head branch is backport-1443-to-0-26-0.