mark `read` as side-effectful

[vemv]

src/refactor_nrepl/extract_definition.clj:17:5: unused-ret-vals: Should use return value of function call, but it is discarded: (read rdr).
src/refactor_nrepl/extract_definition.clj:18:5: unused-ret-vals: Should use return value of function call, but it is discarded: (read rdr).