Revert "Temporarily disable failing zlib tests on travis (php#10738)"

This reverts commit 8c9c678.

Author: bukka

ext/zlib/tests/gzcompress_basic1.phpt

@@ -2,8 +2,6 @@
 Test gzcompress() function : basic functionality
 --EXTENSIONS--
 zlib
---SKIPIF--
-<?php if (getenv('TRAVIS')) die('skip Currently fails on Travis'); ?>
 --FILE--
 <?php
 /*

ext/zlib/tests/gzdeflate_basic1.phpt

@@ -2,8 +2,6 @@
 Test gzdeflate() function : basic functionality
 --EXTENSIONS--
 zlib
---SKIPIF--
-<?php if (getenv('TRAVIS')) die('skip Currently fails on Travis'); ?>
 --FILE--
 <?php
 /*

ext/zlib/tests/gzencode_basic1.phpt

@@ -2,8 +2,6 @@
 Test gzencode() function : basic functionality
 --EXTENSIONS--
 zlib
---SKIPIF--
-<?php if (getenv('TRAVIS')) die('skip Currently fails on Travis'); ?>
 --FILE--
 <?php
 /*