[travis] Remove coverity scan

I never could get it to work, and it's a proprietary platform.

.travis.yml

@@ -10,9 +10,6 @@ env:
     - CFLAGS="-Werror --coverage"
     - CXXFLAGS="-Werror --coverage"
     - LDFLAGS="--coverage"
-    # The next declaration is the encrypted COVERITY_SCAN_TOKEN, created
-    #   via the "travis encrypt" command using the project repo's public key
-    - secure: "RoR4NtzEDTR8QKmLVuy2wN+YGXuq8VcgVvDuFJDdOdIbtX+kQStesJXDcf1y0G1T8Ripjn9JGXBd9eoUwNc8sJpxNwKZBkIPi42FuK6e/cZZRYlgUyi5df0fQJ8VSCDU7OoZJq3pAtTe8mQPeeuk5G7cKRSsJVt8e03K7PQcU6Y="
 install:
   - pip install --user nose
   - pip install --user cpp-coveralls # for coveralls.io code coverage tracking
@@ -37,11 +34,3 @@ addons:
       - libicu-dev # for extra unicode functions
       - libgraphite2-dev # for extra shapers
       - # libgirepository1.0-dev # for gobject-introspection
-  coverity_scan:
-    project:
-      name: "behdad/harfbuzz"
-      description: "Build submitted via Travis CI"
-    notification_email: coverity@behdad.org
-    build_command_prepend: "./configure; make clean"
-    build_command:   "make -j 4"
-    branch_pattern: coverity_scan

README

 [![Build Status](https://travis-ci.org/behdad/harfbuzz.svg)](https://travis-ci.org/behdad/harfbuzz)
 [![Coverage Status](https://img.shields.io/coveralls/behdad/harfbuzz.svg)](https://coveralls.io/r/behdad/harfbuzz)
-[![Coverity Scan](https://img.shields.io/coverity/scan/5450.svg)](https://scan.coverity.com/projects/5450)
 
 This is HarfBuzz, a text shaping library.