Improve adapter content warning documentation

[ehsanestaji]

Clarifies the Adapter Content help page so the documented warning conditions match the implementation.

Changes:

• Explain that warnings are raised when adapter, polyA, or polyG content exceeds 5% at any read position.
• Document that a warning is also raised when reads are shorter than the longest configured adapter sequence.
• Fix the Failure section wording so it says the module fails at the 10% threshold.

Validation:

• xmllint --html --noout 'Help/3 Analysis Modules/10 Adapter Content.html'\n- git diff --check