Apply suggestion from @zachariahcox

Signed-off-by: Zachariah Cox <zachariahcox@github.com>

Author: zachariahcox

docs/spec/draft/source-requirements.md

@@ -287,7 +287,7 @@ attestation.
 
 > For another example, if the organization claims that all consumable Source
 Revisions on the `main` branch were tested prior to acceptance, this MUST be
-explicitly enforced in the SCS, not left to a purely social contract.
+explicitly enforced in the SCS.
 
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