…orflow#6319)

## Motivation for features / changes
tensorflow#6289

## Technical description of changes
new tsne learning rate will take effect during next tsne iteration

## Screenshots of UI changes
N/A

## Detailed steps to verify changes work correctly (as executed by you)
1. Open t-SNE projection
1. Adjust learning rate
1. Verify a small learning rate will stall changes and a large learning
rate will accelerate changes between iterations

## Alternate designs / implementations considered