Build new container image with latest fossa-cli (v3.6.15)

[oxr463]

A new pipeline needs to be kicked off to upgrade the container image to the latest fossa-cli (v3.6.15).

Reference(s):

• https://github.com/fossas/fossa-cli/releases/tag/v3.6.15
• https://github.com/rancherlabs/drone-plugin-fossa/blob/main/Dockerfile#L9

[oxr463]

Ping @ivan-claire or @Anarkis