Update gradle wrapper

gradle/wrapper/gradle-wrapper.properties

@@ -1,22 +1,4 @@
-#
-# Skybot, a multipurpose discord bot
-#      Copyright (C) 2017 - 2018  Duncan "duncte123" Sterken & Ramid "ramidzkh" Khan & Maurice R S "Sanduhr32"
-#
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU Affero General Public License as published
-# by the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU Affero General Public License for more details.
-#
-# You should have received a copy of the GNU Affero General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-#
-
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.5.1-bin.zip
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStorePath=wrapper/dists