Delete Ensembl Data Provider source from igbDefaultPrefs.json

Removed the Ensembl provider from the JSON, here is the updated code: https://bitbucket.org/jaya-sravani/integrated-genome-browser/branch/IGBF-4092. The actual ensembl service code will still be present for any future use.

To Test:

1. Clone the given branch (https://bitbucket.org/jaya-sravani/integrated-genome-browser/branch/IGBF-4092) and build IGB locally.
2. Check the igbDefaultPrefs.json file and search for the Ensembl data provider in it, it shouldn't be present anymore.
3. Check for Ensembl in the Available Data Sources Tab (Click on Configure beside Available Data -> Data Sources Tab), it shouldn't be present anymore.
4. Check whether Ensembl genomes are still visible in the species dropdown, they shouldn't be present anymore. (genomes like: acanthochromis_polyacanthus, electrophorus_electricus), you can compare the dropdown list of this branch IGB to the main branch IGB as well.

Tested on Mac following Sravani's testing instructions. Everything looks good.

Ready for pull request.

Pull request raised: https://bitbucket.org/lorainelab/integrated-genome-browser/pull-requests/1059

Ann Loraine - please merge today

Update:

• PR merged
• New installers built.
• New installers deployed to bioviz.org early access page.

Ready for testing.

Tested on Mac with main branch installer.

• Ensembl is not present in the Available Data Sources tab.
• I do not see any Ensembl genomes in the species dropdown.

Closing ticket.