Remove properties from tf-scalar-card (#627)

PR #626 had added default properties to vz-line-chart, and so we no
longer have to specify them in tf-scalar-card.

Specifically, we remove yValueAccessor and tooltipColumns but keep
the binding for xComponentsCreationMethod. We keep the latter to let
the user change the value on the horizontal axis.

Test Plan: Note that TensorBoard WAI on scalars demo data. Changing
horizontal axis (to wall time or relative) still works.

tensorboard/plugins/scalar/tf_scalar_dashboard/tf-scalar-card.html

@@ -39,8 +39,6 @@
     <tf-line-chart-data-loader
       x-type="[[xType]]"
       x-components-creation-method="[[_xComponentsCreationMethod]]"
-      y-value-accessor="[[_yValueAccessor]]"
-      tooltip-columns="[[_tooltipColumns]]"
       smoothing-enabled="[[smoothingEnabled]]"
       smoothing-weight="[[smoothingWeight]]"
       tooltip-sorting-method="[[tooltipSortingMethod]]"
@@ -234,55 +232,6 @@
           type: Object,
           computed: '_computeXComponentsCreationMethod(xType)',
         },
-
-        _yValueAccessor: {
-          type: Object,
-          readOnly: true,
-          value: () => {
-            return d => d.scalar;
-          },
-        },
-
-        _tooltipColumns: {
-          type: Array,
-          readOnly: true,
-          value: () => {
-            const valueFormatter = ChartHelpers.multiscaleFormatter(
-                ChartHelpers.Y_TOOLTIP_FORMATTER_PRECISION);
-            const formatValueOrNaN =
-                (x) => isNaN(x) ? 'NaN' : valueFormatter(x);
-            return [
-              {
-                title: 'Name',
-                evaluate: (d) => d.dataset.metadata().name,
-              },
-              {
-                title: 'Smoothed',
-                evaluate: (d, statusObject) => formatValueOrNaN(
-                    statusObject.smoothingEnabled ?
-                        d.datum.smoothed : d.datum.scalar),
-              },
-              {
-                title: 'Value',
-                evaluate: (d) => formatValueOrNaN(d.datum.scalar),
-              },
-              {
-                title: 'Step',
-                evaluate: (d) => ChartHelpers.stepFormatter(d.datum.step),
-              },
-              {
-                title: 'Time',
-                evaluate: (d) => ChartHelpers.timeFormatter(d.datum.wall_time),
-              },
-              {
-                title: 'Relative',
-                evaluate:
-                    (d) => ChartHelpers.relativeFormatter(
-                        ChartHelpers.relativeAccessor(d.datum, -1, d.dataset)),
-              },
-            ]
-          },
-        },
       },
       reload() {
         this.$$('tf-line-chart-data-loader').reload();