Fix Databrowser shows correct count of filtered objects

[engel]

No description provided.

[montymxb]

@engel can you elaborate on this? .length should suffice...

[engel]

After upgrading to parse-dashboard 1.1.2 from 1.0.28 I found that after filtering a table, the object count was not calculated correctly anymore. See screenshot.

This PR fixes this by using List.size instead of List.length (as List.length is not defined in the List (Collection) class of the immutable package)

Additionally I found that v1.0.28 includes the "immutable": "~3.7.5" package while v1.1.2 uses "immutable": "~3.8.1".
I assume that changes to the immutable package are the reason why filters.length not work anymore.

[montymxb]

@engel just confirmed this, and went to their docs and found size listed there. I did not find any reference to length however, not sure if that ever was a valid member or not.

[montymxb]

approved! Nice catch on this one.