PEP 518: Fix Sphinx warnings (#4810)

Author: Secrus

peps/pep-0518.rst

@@ -515,9 +515,6 @@ References
 .. [#pip] pip
    (https://pypi.python.org/pypi/pip)
 
-.. [#wheel] wheel
-   (https://pypi.python.org/pypi/wheel)
-
 .. [#toml] TOML
    (https://github.com/toml-lang/toml)
 
@@ -536,9 +533,6 @@ References
 .. [#pypa] PyPA
    (https://www.pypa.io)
 
-.. [#bazel] Bazel
-   (http://bazel.io/)
-
 .. [#ast_literal_eval] ``ast.literal_eval()``
    (https://docs.python.org/3/library/ast.html#ast.literal_eval)