feat: added 'blocklyNotDeletable' class to block_svg

[Shreshthaaa]

Details :
Added blocklyNotDeletable CSS class to block_svg.

Fixes : #8265

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[github-actions]

Welcome! It looks like this is your first pull request in Blockly, so here are a couple of tips:

• You can find tips about contributing to Blockly and how to validate your changes on our developer site.
• All contributors must sign the Google Contributor License Agreement (CLA). If the google-cla bot leaves a comment on this PR, make sure you follow the instructions.
• We use conventional commits to make versioning the package easier. Make sure your commit message is in the proper format or learn how to fix it.
• If any of the other checks on this PR fail, you can click on them to learn why. It might be that your change caused a test failure, or that you need to double-check the style guide.
  Thank you for opening this PR! A member of the Blockly team will review it soon.

[Shreshthaaa]

Hi @BeksOmega, I wanted to check if there's any update or if any further action is needed from my side.
Thank you!

[Shreshthaaa]

Hey @BeksOmega, I have created a new PR for the same issue. Last one had some issues.
Kindly check the new PR.