Few dashboard graph improvements.

web/pgadmin/static/js/Theme/overrides/uplot.override.js

@@ -21,6 +21,7 @@ export default function uplotOverride(theme) {
       borderRadius: theme.shape.borderRadius,
       color: theme.palette.background.default,
       backgroundColor: theme.palette.text.primary,
+      zIndex: 9999,
 
       '& .uplot-tooltip-label': {
         display: 'flex',

web/pgadmin/static/js/components/PgChart/StreamingChart.jsx

@@ -69,6 +69,7 @@ export default function StreamingChart({xRange=75, data, options}) {
       alpha: 0.3,
     },
     cursor: {
+      y: false,
       drag: {
         setScale: false,
       }