swig-py: Remove the obviously busted svn_string_t memberin tyemap.

This typemap can't work with the swig-py bindings becuase _global_pool is not
a global variable like in the other bindings.  We'd need to use _global_py_pool
or ideally handle a passed in pool.  You can see an example patch that should
add this functionality here: http://svn.haxx.se/dev/archive-2014-08/0244.shtml

I'm removing this typemap rather than commiting the above because we don't
actually have a struct with svn_string_t members that we wrap in the Python
bindings.  Recent changes to svn_wc_conflict_description2_t creates one but
the svn_wc_conflict_resolver_func2_t isn't wrapped to make it useful anyway.
So that was added to the ignore list in r1619338.

* subversion/bindings/swig/include/svn_string.swg
  (svn_string_t): Remove the memberin typemap.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1619345 13f79535-47bb-0310-9956-ffa450edef68