Update PageBuilder version in .travis.yml

The /Hieromon/PageBuilder repository's 1.1.0 appears to have been deleted and the only tag now is 1.2.3. This resulted in failure of the Travis CI build:
https://travis-ci.org/per1234/AutoConnect/jobs/474724488#L731

Selected library is not available
The command "arduino --install-library PubSubClient,PageBuilder:1.1.0" failed and exited with 1 during .

.travis.yml

@@ -20,7 +20,7 @@ before_install:
   - if [[ "$BOARD" =~ "esp32:esp32:" ]]; then
       arduino --install-boards esp32:esp32;
     fi
-  - arduino --install-library PubSubClient,PageBuilder:1.1.0
+  - arduino --install-library PubSubClient,PageBuilder:1.2.3
   - buildExampleSketch() { arduino --verbose-build --verify --board $BOARD $PWD/examples/$1/$1.ino; }
 install:
   - mkdir -p ~/Arduino/libraries