Remove Gradle versions which are not supported from the current

com.gradle.plugin-publish plugin

Author: Horcrux7

.travis.yml

@@ -3,10 +3,6 @@ jdk:
   - openjdk8
 env:
   matrix:
-   - LIB_GRADLE_VERSION=2.14.1 DEPLOY=true
-   - LIB_GRADLE_VERSION=3.0 DEPLOY=true
-   - LIB_GRADLE_VERSION=3.1 DEPLOY=true
-   - LIB_GRADLE_VERSION=3.3
    - LIB_GRADLE_VERSION=3.4.1 DEPLOY=true
    - LIB_GRADLE_VERSION=3.5.1
    - LIB_GRADLE_VERSION=4.0.1