docs: Change mention of PII to 'sensitive identifiers' for accuracy

Updates the documentation to use the term 'sensitive identifiers' instead of 'PII' to be more accurate and consistent with the tool's functionality.

Author: aureliuscanon

CONTRIBUTING.md

@@ -79,7 +79,7 @@ privlog .
 
 - `privlog/rules/privlog.yml`
   - **Purpose:** The core Semgrep ruleset, which complements the AST checker.
-  - **Responsibilities:** Defines rules for detecting PII, secrets, and unsafe logging patterns.
+  - **Responsibilities:** Defines rules for detecting sensitive identifiers, secrets, and unsafe logging patterns.
 
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