Update occt version number in INSTALL.md Fix #968

Author: tpaviot

INSTALL.md

@@ -20,9 +20,9 @@ pythonOCC needs the following libraries or programs to be installed before you
 can compile/use it :
 
 *   the python programming language (<http://www.python.org>). Python 3.x is required. Python 2
-is officially dropped since the release 7.4.0.
+is officially dropped since the release 7.5.0.
 
-*   OpenCascade 7.4.0 (<https://dev.opencascade.org>),
+*   OpenCascade 7.5.0 (<https://dev.opencascade.org>),
 
 *   SWIG 3.0.11 or higher (<http://www.swig.org>),