Revert "travis-ci - build linux AppImage with version string for v3.5…

… release"

This reverts commit c6691bf.
[skip ci]

travis/linux/before_script.sh

@@ -6,8 +6,6 @@ cp qwt/qwtconfig.pri.in qwt/qwtconfig.pri
 cp src/gcconfig.pri.in src/gcconfig.pri
 # Define GC version string, only for tagged builds
 if [ -n "$TRAVIS_TAG" ]; then echo DEFINES += GC_VERSION=VERSION_STRING >> src/gcconfig.pri; fi
-# Temporary hack to get a build with 3.5 version string without a new TAG
-echo DEFINES += GC_VERSION=VERSION_STRING >> src/gcconfig.pri;
 # user WEBENGINE
 echo DEFINES += NOWEBKIT >> src/gcconfig.pri
 # Trusty needs C99 mode to enable declarations in for loops