fix(datatable): search not working with uppercase characters in query (…

…carbon-design-system#11493)

### Related Ticket(s)

Closes carbon-design-system#11483

### Description

Search is not working as expected with uppercase characters in query string.

### Changelog

**Changed**

- Updated the search logic to convert the query string as well as the main string to lowercase and then compare.

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web-components/packages/carbon-web-components/src/components/data-table/table.ts

@@ -168,7 +168,7 @@ class CDSTable extends HostListenerMixin(LitElement) {
    */
   @property()
   filterRows = (rowText: string, searchString: string) =>
-    rowText.toLowerCase().indexOf(searchString) < 0;
+    rowText.toLowerCase().indexOf(searchString.toLowerCase()) < 0;
 
   /**
    * The total headers