Remove reader_parse_test/translate_module fuzz targets (#1212)

This commit removes the two fuzz targets that we imported from cranelift
when cranelift merged in. These have both uncovered a few issues in the
fuzz targets themselves, for example:

* `translate_module` - this doesn't verify the wasm is valid a head of
  time and cranelift is known to panic on translating invalid wasm
  modules. We also already do a lot of fuzzing of translation of wasm
  modules, so this isn't necessarily buying us anything over what we're
  already fuzzing.

* `reader_parse_test` - discovered in #1205 we already found some "bugs"
  in this but it may not necessarily rise to the level of "needs to be
  run on oss-fuzz for us to find more bugs" yet. It looks like this is
  still somewhat internal so we can re-enable when we've got folks to
  fix the fuzz bugs coming in.

Closes #1205

fuzz/Cargo.toml

@@ -46,15 +46,3 @@ name = "differential"
 path = "fuzz_targets/differential.rs"
 test = false
 doc = false
-
-[[bin]]
-name = "translate_module"
-path = "fuzz_targets/translate_module.rs"
-test = false
-doc = false
-
-[[bin]]
-name = "reader_parse_test"
-path = "fuzz_targets/reader_parse_test.rs"
-test = false
-doc = false