clonebundle: use 'repo.vfs' instead of 'repo.opener'

The later is a 5 years old form.

hgext/clonebundles.py

@@ -177,7 +177,7 def capabilities(orig, repo, proto):
     # Only advertise if a manifest exists. This does add some I/O to requests.
     # But this should be cheaper than a wasted network round trip due to
     # missing file.
-    if repo.opener.exists('clonebundles.manifest'):
+    if repo.vfs.exists('clonebundles.manifest'):
         caps.append('clonebundles')
 
     return caps

mercurial/wireproto.py

@@ -736,7 +736,7 def clonebundles(repo, proto):
     depending on the request. e.g. you could advertise URLs for the closest
     data center given the client's IP address.
     """
-    return repo.opener.tryread('clonebundles.manifest')
+    return repo.vfs.tryread('clonebundles.manifest')
 
 wireprotocaps = ['lookup', 'changegroupsubset', 'branchmap', 'pushkey',
                  'known', 'getbundle', 'unbundlehash', 'batch']