Remove outdated 'wrapper' task from build.gradle (#907)

[PhilipRoman]

Fixes #907

Description

The issue and solution is described here: https://stackoverflow.com/questions/53709282/cannot-add-task-wrapper-as-a-task-with-that-name-already-exists

git blame shows that build.gradle was last modified in 2013: c2e7493 and therefore uses a very old version of Gradle (1.4). Since Gradle wrapper isn't currently tracked in the git repo (maybe it should be?), I simply deleted the whole 'wrapper' block.

Related Issue

#907

Motivation and Context

The current build.gradle file is outdated and produces errors when used with modern Gradle versions.

How Has This Been Tested?

Building with Gradle 5+ now works as expected.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.