shallowrepo: remove backwards compat code that predates in-tree remotefilelog

Differential Revision: https://phab.mercurial-scm.org/D6538

hgext/remotefilelog/shallowrepo.py

@@ -33,13 +33,6 b' from . import ('
     shallowutil,
 )
 
-if util.safehasattr(util, '_hgexecutable'):
-    # Before 5be286db
-    _hgexecutable = util.hgexecutable
-else:
-    from mercurial.utils import procutil
-    _hgexecutable = procutil.hgexecutable
-
 # These make*stores functions are global so that other extensions can replace
 # them.
 def makelocalstores(repo):
@@ -192,7 +185,7 b' def wraprepo(repo):'
                                opts=None):
             """Runs prefetch in background with optional repack
             """
-            cmd = [_hgexecutable(), '-R', repo.origroot, 'prefetch']
+            cmd = [procutil.hgexecutable(), '-R', repo.origroot, 'prefetch']
             if repack:
                 cmd.append('--repack')
             if revs: