Update documentation with warning about multiple families when scoring compounds

[fellen31]

Description

While this PR does not really fix issue 148, it at least adds a warning in the documentation.

How to prepare for test

• Ssh to relevant server (depending on type of change)
• Use stage: us
• Paxa the environment: paxa
• Install on stage (example for Hasta):

  bash /home/proj/production/servers/resources/hasta.scilifelab.se/update-tool-stage.sh -e S_[TOOL]-t [TOOL] -b [THIS-BRANCH-NAME] -a

How to test

• Do ...

Expected test outcome

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• Take a screenshot and attach or copy/paste the output.

Review

• Tests executed by
• "Merge and deploy" approved by
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This version is a

• MAJOR - when you make incompatible API changes
• MINOR - when you add functionality in a backwards compatible manner
• PATCH - when you make backwards compatible bug fixes or documentation/instructions

Implementation Plan

• Document in ...
• Deploy this branch on ...
• Inform to ...