[FAB-9941] Remove :ref: to gone "upgrade-vendored-shim"

From enable_tls.rst, drop the sentence containing a :ref: to the
now non-existent label "upgrade-vendored-shim", which once existed
in the file "upgrade_to_one_point_one.rst", but was tossed by
commit 35c1978.

If there truly needs to be such a reference, those files will
need rewriting.

Change-Id: I8b6a3453874ef13083edf3ea20fb240f887137be
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

docs/source/enable_tls.rst

@@ -139,8 +139,7 @@ If you see the error message ``remote error: tls: bad certificate`` in your chai
 ensure that your chaincode has been built using the chaincode shim provided with Fabric v1.1
 or newer. If your chaincode does not contain a vendored copy of the shim, deleting the
 chaincode container and restarting its peer will rebuild the chaincode container using the
-current shim version. If your chaincode vendored a previous version of the shim, review the
-documentation on how to :ref:`upgrade-vendored-shim`.
+current shim version.
 
 .. Licensed under Creative Commons Attribution 4.0 International License
    https://creativecommons.org/licenses/by/4.0/