Update Spark 2.x dependency version to 2.4.7

[heuermh]

No description provided.

[AmplabJenkins]

Test FAILed.
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Build result: FAILURE

[...truncated 5 lines...]Cloning the remote Git repositoryCloning repository https://github.com/bigdatagenomics/adam.git > git init /home/jenkins/workspace/ADAM-prb # timeout=10Fetching upstream changes from https://github.com/bigdatagenomics/adam.git > git --version # timeout=10 > git fetch --tags --progress https://github.com/bigdatagenomics/adam.git +refs/heads/:refs/remotes/origin/ # timeout=15 > git config remote.origin.url https://github.com/bigdatagenomics/adam.git # timeout=10 > git config --add remote.origin.fetch +refs/heads/:refs/remotes/origin/ # timeout=10 > git config remote.origin.url https://github.com/bigdatagenomics/adam.git # timeout=10Fetching upstream changes from https://github.com/bigdatagenomics/adam.git > git fetch --tags --progress https://github.com/bigdatagenomics/adam.git +refs/pull/:refs/remotes/origin/pr/ # timeout=15 > git rev-parse origin/pr/2277/merge^{commit} # timeout=10 > git branch -a -v --no-abbrev --contains 0e441bf # timeout=10Checking out Revision 0e441bf (origin/pr/2277/merge) > git config core.sparsecheckout # timeout=10 > git checkout -f 0e441bf36dd7b15678ef14de38f63344773f9079First time build. Skipping changelog.Triggering ADAM-prb ? 2.7.5,2.12,3.0.1,ubuntuTriggering ADAM-prb ? 2.7.5,2.11,2.4.7,ubuntuTriggering ADAM-prb ? 2.7.5,2.12,2.4.7,ubuntuADAM-prb ? 2.7.5,2.12,3.0.1,ubuntu completed with result SUCCESSADAM-prb ? 2.7.5,2.11,2.4.7,ubuntu completed with result FAILUREADAM-prb ? 2.7.5,2.12,2.4.7,ubuntu completed with result FAILURENotifying endpoint 'HTTP:https://webhooks.gitter.im/e/ac8bb6e9f53357bc8aa8'
Test FAILed.

[AmplabJenkins]

Test PASSed.
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Test PASSed.