Revert invalid masonry selector to fix edge cases in Space view

[bodom0015]

Description

Problem

The columnWidth property apparently tells masonry a selector that defines a single column. Setting these to the same value cause a couple of other issues. Only the itemSelector should have been modified.

Approach

Revert a line from #11 that should not have been modified.

How to Test

Setup:

1. Checkout and run this branch locally
2. Login to Clowder and create a Space
3. Add 2 datasets to this space

Case A: No preview images

Prerequisites: no image previews attached to any files or dataset in the Space

1. View the Space in Clowder
   • You should see that the Dataset cards no longer overlap with the Collections section below

Case B: With preview images

1. Run the image-preview extractor and upload an image file to one or more of the datasets
   • This should attach an image preview to the dataset
2. View the Space in Clowder
   • You should see that the Dataset cards are now stacked horizontally and vertically, instead of only vertically

Review Time Estimate

• Immediately
• Within one week
• When possible

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 change requires a change to the documentation. N / A
• I have updated the CHANGELOG.md. N / A
• I have signed the CLA
• I have updated the documentation accordingly. N / A
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes. N / A
• All new and existing tests passed.

[lmarini]

Thank you!