removed gzstd test from travis

this target does no longer exist
diff --git a/.travis.yml b/.travis.yml
index ba9f996..90306da 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -33,7 +33,7 @@
 
 
     # Standard Ubuntu 12.04 LTS Server Edition 64 bit
-    - env: Ubu=12.04 Cmd="make -C programs zstd-small zstd-decompress zstd-compress && make -C tests test-gzstd && make -C programs clean && make -C tests versionsTest"
+    - env: Ubu=12.04 Cmd="make -C programs zstd-small zstd-decompress zstd-compress && make -C programs clean && make -C tests versionsTest"
       os: linux
       sudo: required