Allow composer/installers to execute code / tmp/Plugin: file does not exist

[Kagee]

This appears to be the correct fix for this new error

...

composer/installers contains a Composer plugin which is blocked by your allow-plugins config. 
You may add it to the list if you consider it safe. See https://getcomposer.org/allow-plugins
You can run "composer config --no-plugins allow-plugins.composer/installers [true|false]" to 
enable it (true) or keep it disabled and suppress this warning (false)

...

Step 36/55 : COPY --from=composer-build /tmp/Vendor /var/www/MISP/app/Vendor
 ---> 7f6834a577d1
Step 37/55 : COPY --from=composer-build /tmp/Plugin /var/www/MISP/app/Plugin
COPY failed: stat tmp/Plugin: file does not exist

https://getcomposer.org/doc/06-config.md#allow-plugins