[find] Remove find extension

[jiasli]

Similar to #1251 [managementgroups] Remove managementgroups extension

find command is already in the main CLI.

This PR removes the whole find extension to prevent the doc from being generated and further download from customers.

[azuresdkci]

If this PR is for a new extension or change to an existing extension, use the following to try out the changes in this PR:

docker run -it microsoft/azure-cli:latest
export EXT=<NAME>
pip install --upgrade --target ~/.azure/cliextensions/$EXT "git+https://github.com/jiasli/azure-cli-extensions.git@remove-find#subdirectory=src/$EXT&egg=$EXT"

[mirdaki]

I've added the extension suppression in this PR.