Travis release: Read API key from variable

secure key was probably removed. Read from travis ci env variable
instead

.travis.yml

@@ -46,8 +46,9 @@ deploy:
   # - Create a `public_repo` GitHub token. Go to: https://github.com/settings/tokens/new
   # - Encrypt it: `travis encrypt 0123456789012345678901234567890123456789
   # - Paste the output down here
-  api_key:
-    secure: UlU73Td7Bkb2N88ws4YGLWR+4U0IMgiou9QQtMnmpouJFjeUNxtLSPMPODVXP7zq4sKt5HR5B3fX9MW4mKm351fvnQEoihETn06pKiXGnY//SlTPTt67MX9ZOYmd9ohJReMDOZDgqhnGLxfymycGtsLAmdjDZnAl+IMqgg0FMyVFj9Cl9aKxnn12lxQyX4zabHKk8TUKD3By8ZoEUnJMHt3gEtOmbDgS4brcTPeHCzqnYFw73LEnkqvz+JP0XwauJY7Cf8lminKm/klmjCkQji8T9SHI52v1g0Fxpx0ucp2o3vulQrLHXaHvZ6Fr7J0cSXXzaFF3rrGLt4t4jU/+9TZm1+n5k5XuPW4x4NTCC9NmIj/z0/z41t82E9qZhzhtm2Jdsg6H2tNk+C774TYqcmR6GCvfRadfjRp3cA5dh0UwDVjH2MJFxlHDVkl6la0mVVRsCGF3oBKZVk0BDl1womfnmI46o/uU+gLknHN6Ed6PHHPPYDViWd3VKdmHKT7XrkMMUF6HjZUtla689DWIOWZSiV++1dVPcl/1TV+6tTmN4bBtPcLuX7SHRuLp2PI2kATvRMECsa7gZRypW4jKpVn7b2yetX9TVI3i1zR5zkQJ3dPg8sATvYPL53aKH/WsqUg4rzoAlbk9so+++R4bQY69LhV3B511B7EAynoZFdM
+#  api_key:
+#    secure: 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
+  api_key: $API_KEY
   file_glob: true
   file: $CRATE_NAME-$TRAVIS_TAG-$TARGET.*
   on: