PEP 8011: Fix links to footnotes (python#818)

pep-8011.rst

@@ -55,7 +55,7 @@ Roles and responsibilities of the leadership trio
 - Understand their own limitation, and seek advice whenever necessary.
 - Provide mentorship to the next generation of leaders.
 - Be a Python core developer
-- Be a voting member of The PSF (one of Contributing / Manager / Fellow / Supporter). [2]
+- Be a voting member of The PSF (one of Contributing / Manager / Fellow / Supporter). [2]_
 - Understand that Python is not just a language but also a community. They need
   to be aware of issues in Python not just the technical aspects, but also
   other issues in the community.
@@ -120,9 +120,9 @@ can begin, and the voting mechanism described in PEP 8001 will be used.
 Qualities desired out of the trio:
 
 - Be a Python core developer.
-- Be a voting PSF member (one of Contributing / Manager / Fellow / Supporter). [2]
+- Be a voting PSF member (one of Contributing / Manager / Fellow / Supporter). [2]_
 - Be a member of the community with good standing.
-- Adhere to The PSF's code of conduct (Be open, considerate, and respectful). [1]
+- Adhere to The PSF's code of conduct (Be open, considerate, and respectful). [1]_
 - Be willing to accept the said roles and responsibilities.
 - Able to communicate and articulate their thoughts effectively.
 
@@ -313,7 +313,7 @@ Ideally, the workgroup members should include and reflect the diversity of
 the wider Python community.
 
 Members of this workgroup do not need to be a Python core developer, but they
-need to be at least a basic member of the PSF [2].
+need to be at least a basic member of the PSF [2]_.
 
 These workgroup are active as long as the trio are active.
 
@@ -351,7 +351,7 @@ The PSF's mission and diversity statement.
 By being a member of The PSF, Python core developers declare their support for
 Python and agree to the community Code of Conduct.
 
-For more details of The PSF membership, see: PSF Membership FAQ [2].
+For more details of The PSF membership, see: PSF Membership FAQ [2]_.
 
 Reasoning for choosing the name trio
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