Remove deprecated sdist reinstall feature for 21.2

Author: uranusjr

news/10199.removal.rst

@@ -0,0 +1,3 @@
+New resolver: A source distribution is no longer re-installed automatically if
+the currently installed has the same version number. This behaviour has been
+deprecated since pip 20.3.

src/pip/_internal/resolution/resolvelib/resolver.py

@@ -19,7 +19,6 @@
     PipDebuggingReporter,
     PipReporter,
 )
-from pip._internal.utils.deprecation import deprecated
 from pip._internal.utils.filetypes import is_archive_file
 
 from .base import Candidate, Requirement
@@ -141,19 +140,8 @@ def resolve(
                     and candidate.source_link.ext != ".zip"
                 )
                 if looks_like_sdist:
-                    # is a local sdist -- show a deprecation warning!
-                    reason = (
-                        "Source distribution is being reinstalled despite an "
-                        "installed package having the same name and version as "
-                        "the installed package."
-                    )
-                    replacement = "use --force-reinstall"
-                    deprecated(
-                        reason=reason,
-                        replacement=replacement,
-                        gone_in="21.2",
-                        issue=8711,
-                    )
+                    # is a local sdist -- skip
+                    continue
 
                 # is a local sdist or path -- reinstall
                 ireq.should_reinstall = True