Do not over-prune var data cache (#1198)

* Remove unused variables and imports

* Simplify conditional

* Fix typo

* Do not overprune var data cache

There is a bug in how the universe and world gene sets are constructed
and passed to `ControlsHelpers.pruneVarDataCache` that causes the var
data cache to be over-pruned. This commit fixes the issue.

Consider the following example from the node console:

```
❯ node
Welcome to Node.js v13.5.0.
Type ".help" for more information.
> new Set([1], [2], [3])
Set(1) { 1 }
```

What we really want is the set `Set(3) { 1, 2, 3 }`, which can be
constructed as:

```
> new Set([].concat([1], [2], [3]))
Set(3) { 1, 2, 3 }
```

client/src/util/stateManager/controlsHelpers.js

@@ -172,7 +172,7 @@ export function pruneVarDataCache(varData, needed) {
   */
 
   /*
-  VarDataCacheLowWatermark - this cofig value sets the minimum cache size,
+  VarDataCacheLowWatermark - this config value sets the minimum cache size,
   in columns, below which we don't throw away data.
 
   The value should be high enough so we are caching the maximum which will