Update gradle to version 5.5.1 (timols#358)

Author: tristanlins

build.gradle

@@ -56,10 +56,6 @@ task sourcesJar(type: Jar, dependsOn:classes) {
 
 artifacts { archives sourcesJar }
 
-task wrapper(type: Wrapper) {
-    gradleVersion = "4.6"
-}
-
 test {
     useJUnitPlatform {
         includeEngines 'junit-jupiter'

gradle/wrapper/gradle-wrapper.jar

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.5.1-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists