Make the Clip button primary (blue) (#1181)

Fixes https://github.com/chanzuckerberg/cellxgene/issues/1101

I can't reproduce the active/inactive issue described in #1101

The only change remaining in #1101 is to make the clip button blue.
This commit makes that change.

client/src/components/menubar/clip.js

@@ -116,7 +116,7 @@ function Clip(props) {
               <Button
                 type="button"
                 data-testid="clip-commit"
-                className="bp3-button"
+                intent="primary"
                 disabled={isClipDisabled()}
                 style={{
                   cursor: "pointer",