JAVA-2844: Revert gradle upgrade

After the upgrade from Gradle 4.5.1 to 4.7, we're no longer able
to release the driver, as the uploadArchives task uploads to the
Sonatype snapshot repository rather than the staging repository even
when the version does not end with "-SNAPSHOT".

Reverting this change until we can determine the root cause.

Author: jyemin

build.gradle

@@ -315,7 +315,7 @@ def setJavaDocOptions(MinimalJavadocOptions options) {
 // Root project configuration           //
 //////////////////////////////////////////
 task wrapper(type: Wrapper) {
-    gradleVersion = '4.7'
+    gradleVersion = '4.5.1'
 }
 
 gradle.buildFinished { BuildResult result ->

gradle/wrapper/gradle-wrapper.jar

@@ -1,20 +1,5 @@
-#
-# Copyright 2008-present MongoDB, Inc.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#   http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-#
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.5.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.7-bin.zip