sheets: Update ExtendedValue Fields to be pointer

Currently users are unable to tell if values are default or not
set.

Fixes: #474
Change-Id: I9e2d107fc4045ad88f4a0049c6ad985bc76f19be
Reviewed-on: https://code-review.googlesource.com/c/google-api-go-client/+/56630
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Tyler Bui-Palsulich <tbp@google.com>
diff --git a/google-api-go-generator/gen.go b/google-api-go-generator/gen.go
index 7bf2c3b..96bc906 100644
--- a/google-api-go-generator/gen.go
+++ b/google-api-go-generator/gen.go
@@ -980,6 +980,10 @@
 	{api: "servicecontrol:v1", schema: "MetricValue", field: "DoubleValue"},
 	{api: "servicecontrol:v1", schema: "MetricValue", field: "Int64Value"},
 	{api: "servicecontrol:v1", schema: "MetricValue", field: "StringValue"},
+	{api: "sheets:v4", schema: "ExtendedValue", field: "BoolValue"},
+	{api: "sheets:v4", schema: "ExtendedValue", field: "FormulaValue"},
+	{api: "sheets:v4", schema: "ExtendedValue", field: "NumberValue"},
+	{api: "sheets:v4", schema: "ExtendedValue", field: "StringValue"},
 	{api: "slides:v1", schema: "Range", field: "EndIndex"},
 	{api: "slides:v1", schema: "Range", field: "StartIndex"},
 	{api: "sqladmin:v1beta4", schema: "Settings", field: "StorageAutoResize"},