ZEPPELIN-2137 Changed "show line chart with focus" to "zoom"

https://issues.apache.org/jira/browse/ZEPPELIN-2137

Improvement

### How should this be tested?
Run it, look at it (UX change)

### Screenshots (if appropriate)

### Questions:
* Does the licenses files need update?
* Is there breaking changes for older versions?
* Does this needs documentation?

Author: samthebest <samthebest@users.noreply.github.com>

Closes #2050 from samthebest/master and squashes the following commits:

9f68fcd [samthebest] ZEPPELIN-2137 WS commit to try to force rerun of CI checks
89467ab [samthebest] ZEPPELIN-2137 WS commit to try to force rerun of CI checks
96362ab [samthebest] ZEPPELIN-2137 Changed "show line chart with focus" to "zoom"

zeppelin-web/src/app/visualization/builtins/visualization-linechart.js

@@ -100,7 +100,7 @@ export default class LinechartVisualization extends Nvd3ChartVisualization {
           <input type="checkbox"
                ng-model="config.lineWithFocus"
                ng-click="save()" />
-          show line chart with focus
+          zoom
         </label>
       </div>`,
       scope: {