Fix 'push_artifacts' invocation - remove backslashes

The YAML string literal notation used strips newlines, so there is no
need for backslashes.

.travis.yml

@@ -19,9 +19,14 @@ script:
 
 after_success:
   - ./push_artifacts/git_config_kaitai_bot
-  - ./push_artifacts/publish \
-      -o kaitai-io \
-      -r ide-kaitai-io.github.io \
-      -d "$([ "$TRAVIS_BRANCH" != stable ] && echo devel)" \
-      -m "Regen $TRAVIS_BRANCH kaitai-io/kaitai_struct_webide@$TRAVIS_COMMIT" \
-      -- --exclude=.git --exclude=CNAME --exclude=.nojekyll --exclude=devel out/
+  - ./push_artifacts/publish
+      -o kaitai-io
+      -r ide-kaitai-io.github.io
+      -d "$([ "$TRAVIS_BRANCH" != stable ] && echo devel)"
+      -m "Regen $TRAVIS_BRANCH kaitai-io/kaitai_struct_webide@$TRAVIS_COMMIT"
+      --
+      --exclude=.git
+      --exclude=CNAME
+      --exclude=.nojekyll
+      --exclude=devel
+      out/