Embedding Projector: fix umapNeighbors in bookmark (#6296)

* Motivation for features / changes
number of neighbors isn't stored properly in bookmark

* Technical description of changes
fix bookmark value

* Screenshots of UI changes

* Detailed steps to verify changes work correctly (as executed by you)

* Alternate designs / implementations considered

Author: alicialics

tensorboard/plugins/projector/vz_projector/vz-projector-projections-panel.ts

@@ -315,6 +315,7 @@ class ProjectionsPanel extends LegacyElementMixin(PolymerElement) {
     bookmark.tSNEis3d = this.tSNEis3d;
     // UMAP
     bookmark.umapIs3d = this.umapIs3d;
+    bookmark.umapNeighbors = this.umapNeighbors;
     // custom
     bookmark.customSelectedSearchByMetadataOption =
       this.customSelectedSearchByMetadataOption;