build/sage_bootstrap/uninstall.py: Do not override the stamp file loc…

…ation from environment variable

build/sage_bootstrap/uninstall.py

@@ -14,9 +14,10 @@
 
     2) New-style uninstallation: More recently installed packages that were
        installed with staged installation have a record of all files installed
-       by that package.  That file is stored in the $SAGE_SPKG_INST directory
-       (typically $SAGE_LOCAL/var/lib/sage/installed) and is created when the
-       spkg is installed.  This is a JSON file containing some meta-data about
+       by that package.  That file is stored in the directory
+       $SAGE_LOCAL/var/lib/sage/installed or $SAGE_VENV/var/lib/sage/installed
+       and is created when the spkg is installed.
+       This is a JSON file containing some meta-data about
        the package, including the list of all files associated with the
        package.  This script removes all these files, including the record
        file.  Any directories that are empty after files are removed from them
@@ -57,7 +58,6 @@ def uninstall(spkg_name, sage_local, keep_files=False, verbose=False):
     # The default path to this directory; however its value should be read
     # from the environment if possible
     spkg_inst = pth.join(sage_local, 'var', 'lib', 'sage', 'installed')
-    spkg_inst = os.environ.get('SAGE_SPKG_INST', spkg_inst)
 
     # Find all stamp files for the package; there should be only one, but if
     # there is somehow more than one we'll work with the most recent and delete