Bug 1421491 - Style fixes in Netmonitor r=Honza

Changed CSS to fix selected row style and removed underline for tree headers

MozReview-Commit-ID: hnmnATPSAw
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Bug 1421491 - Style fixes in Netmonitor
Updated CSS Styles to fix issues mentioned in the bug

MozReview-Commit-ID: 7ElhjWmTEgM
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Bug 1421491 - Minor style fixes in netmonitor
Updated CSS to fix style issues in the Bug

--HG--
extra : rebase_source : d0f01d6bd7133b07c66a767d899d93e363dae857

devtools/client/netmonitor/src/assets/styles/NetworkDetailsPanel.css

@@ -141,6 +141,14 @@
   color: var(--string-color);
 }
 
+.network-monitor .tree-container .treeTable .treeValueCell input:focus {
+  color: var(--theme-selection-color) !important;
+}
+
+.network-monitor .tree-container .treeTable .treeRow.hasChildren > .treeLabelCell > .treeLabel:hover {
+  text-decoration: none;
+}
+
 /* Source editor in tab panels */
 
 /* If there is a source editor shows up in the last row of TreeView,