PEP 668: Fix links to other PEPs (#2058)

pep-0668.rst

@@ -98,10 +98,10 @@ package
 Python-specific package manager
     A tool for installing, upgrading, and/or removing Python packages
     in a manner that conforms to Python packaging standards (such as
-    PEP 376 [#PEP-376]_ and PEP 427 [#PEP-427]_). The most popular
-    Python-specific package manager is pip [#pip]_; other examples
-    include the old Easy Install command [#easy-install]_ as well as
-    direct usage of a ``setup.py`` command.
+    PEP 376 and PEP 427). The most popular Python-specific package
+    manager is pip [#pip]_; other examples include the old Easy
+    Install command [#easy-install]_ as well as direct usage of a
+    ``setup.py`` command.
 
     (Conda [#conda]_ is a bit of a special case, as the ``conda``
     command can install much more than just Python packages, making it
@@ -114,12 +114,12 @@ distro package manager
     packages in an installed instance of that distro, which is capable
     of installing Python packages as well as non-Python packages, and
     therefore generally has its own database of installed software
-    unrelated to PEP 376 [#PEP-376]. Examples include ``apt``,
-    ``dpkg``, ``dnf``, ``rpm``, ``pacman``, and ``brew``. The salient
-    feature is that if a package was installed by a distro package
-    manager, removing or upgrading it in a way that would satisfy a
-    Python-specific package manager will generally leave a distro
-    package manager in an inconsistent state.
+    unrelated to PEP 376. Examples include ``apt``, ``dpkg``, ``dnf``,
+    ``rpm``, ``pacman``, and ``brew``. The salient feature is that if
+    a package was installed by a distro package manager, removing or
+    upgrading it in a way that would satisfy a Python-specific package
+    manager will generally leave a distro package manager in an
+    inconsistent state.
 
     This document also uses phrases like "external package manager" or
     "system's package manager" to refer to a distro package manager in
@@ -886,7 +886,7 @@ non-virtual-environment installs in any Python installation, but that
 is outside the scope of this PEP.)
 
 Should the file be TOML? TOML is gaining popularity for packaging (see
-e.g. PEP-517) but does not yet have an implementation in the standard
+e.g. PEP 517) but does not yet have an implementation in the standard
 library. Strictly speaking, this isn't a blocker - distros need only
 write the file, not read it, so they don't need a TOML library (the
 file will probably be written by hand, regardless of format), and
@@ -1078,12 +1078,6 @@ discussion thread `Playing nice with external package managers`_.
 
 .. _`Playing nice with external package managers`: https://discuss.python.org/t/playing-nice-with-external-package-managers/1968
 
-.. [#PEP-376] PEP 376, Database of Installed Python Distributions, Ziadé
-   (http://www.python.org/dev/peps/pep-0376)
-
-.. [#PEP-427] PEP 427, The Wheel Binary Package Format 1.0, Holth
-   (http://www.python.org/dev/peps/pep-0427)
-
 .. [#pip] https://pip.pypa.io/en/stable/
 
 .. [#easy-install] https://setuptools.readthedocs.io/en/latest/deprecated/easy_install.html