docs(samples): update querypagination sample (#2074)

- Updated example to loop through all remaining pages Changes for the open issue: #2073

Author: AyushWalekar

samples/snippets/src/main/java/com/example/bigquery/QueryPagination.java

@@ -62,19 +62,11 @@ public static void queryPagination(String datasetName, String tableName, String
  .getValues()
  .forEach(row -> row.forEach(val -> System.out.printf("%s,\n", val.toString())));
 
- if (results.hasNextPage()) {
- // Next Page
- results
- .getNextPage()
- .getValues()
- .forEach(row -> row.forEach(val -> System.out.printf("%s,\n", val.toString())));
- }
-
- if (results.hasNextPage()) {
+ while (results.hasNextPage()) {
  // Remaining Pages
+ results = results.getNextPage();
  results
- .getNextPage()
- .iterateAll()
+ .getValues()
  .forEach(row -> row.forEach(val -> System.out.printf("%s,\n", val.toString())));
  }