Dont test on ocaml 4.10, as all ppxlib is not available for this version just yet

Author: andersfugmann

.travis.yml

@@ -20,7 +20,6 @@ env:
   - PACKAGE="ppx_protocol_conv_jsonm"     OCAML_VERSION=4.08
   - PACKAGE="ppx_protocol_conv_json"      OCAML_VERSION=4.08 TEST=false
   - PACKAGE="ppx_protocol_conv"           OCAML_VERSION=4.09
-  - PACKAGE="ppx_protocol_conv"           OCAML_VERSION=4.10
 
 os:
   - linux