Remove .travis.yml as it's hardcoded to the old www3 server

We should migrate this to GitLab CI at some point.

.travis.yml

-language: java
-before_install:
-- rvm install 2.4.1
-- gem install travis-custom-deploy
-script: mvn -f org.eventb.texteditor.parent/pom.xml clean verify
-after_success:
-- travis-custom-deploy sftp org.eventb.texteditor.repository/target/repository/
-env:
-  global:
-  - secure: J19wt8RgIJ4rS+g+zx1VD67yqliO4zs2CO1TAHGBgRcwie6uUfqqLU/4Qmpedie8CwQQ/cktHx4C5gL9MbNwiDUVZ2PbdwnyEQ5rdTJpIfxgsDkL+c5mL1rUq/SrnmRTF2PRpt4Ktp5cgZtwH5UH5RUCO/JuVWAzD9TUWbqw0ec=
-  - secure: wIToXAHi6kQpv3a0JfOI35Hd3/16kK/OPdLPizObqFDG+coyZW4URnXm324qGth/iL/JZMt2ffgK7drAumMUWkSEFyvOPphaw7E39g67KX6ZcgMy2Ei9FpoF2kK39KVxSA00rzGlkjoSzLmyiVnQqX2frAEvEk9m/aOx2HlyxDM=
-  - secure: dBIRkrKPtqfu26Nxl7hG+pY9HF96cbifkt/JnrkXvdP/bauQ5iSFF+Nl2TCfDrSGyGyq1DoIFv1EBT3K1KR+3YAFDSPp5sxhVRc3amhAaqngf9Oh9PGsuIvi9WtalNGKEEj6ykmuDI9DAaqsXCP4SY3PjHfw6YksQ0Hz9bdXOFs=
-  - secure: bvQ4nd/bCARliaU+bDOZlsRykcutQcgUaq+Ns4oFkYlkyJ0XsMQPhbMWm/rQy2aOiJLIo9R+4e3+hn1vxmx5hDlzs4BzU8cK3x7hxBxjPx0HeAhWj2aQdyEsNAiDqhd/q5n25Y/lrKRGt1K0HIoaG1rZnOEekVSN0sWLlepexXo=
-notifications:
-  slack:
-    secure: hjNOQo2XuvLc57VjYyYZ+V7GipbnT/gYqPZMC/nQLEOjp5eUWq/J8L8kgmMwy0lWZDUGBc2umIKox1PoovWCUrvYuElkO7Xh7qns2KCVbsxPo9Wc7lmu9idalPrGqry7sLsVGtclARYNEu18vdAb362Gv4+vhc6ZOXYztUfXGWE=