Update all mbed test packages.

This change allows the latest releases of mbed-ls, mbed-host-tests, and
mbed-greentea. This brings new target support, features, and bug fixes.

Author: bridadan

requirements.txt

@@ -13,9 +13,9 @@ pyserial>=3,<=3.4
 Jinja2>=2.7.3,<=2.10
 intelhex>=1.3,<=2.2.1
 intervaltree>=2,<3
-mbed-ls>=1.5.1,<1.7
-mbed-host-tests>=1.4.4,<=1.5
-mbed-greentea>=0.2.24,<=1.5
+mbed-ls>=1.5.1,<1.8
+mbed-host-tests>=1.4.4,<1.6
+mbed-greentea>=0.2.24,<1.7
 beautifulsoup4>=4,<=4.6.3
 fuzzywuzzy>=0.11,<=0.17
 pyelftools>=0.24,<=0.25