chore(sidekick/rust): Improvements in RPC sample generation (#3520)

This includes:

- Fixing one typo in sidekick documentation found by @coryan 
- Applying one import suggestion made by @dbolduc

Author: amanda-tarafa

internal/sidekick/api/model.go

@@ -388,7 +388,7 @@ type AIPStandardGetInfo struct {
 }
 
 // AIPStandardGetInfo returns information relevant to a get operation that is like
-// a get operation as defined by AIP-131, if the method is such and operation.
+// a get operation as defined by AIP-131, if the method is such an operation.
 func (m *Method) AIPStandardGetInfo() *AIPStandardGetInfo {
 	// A get operation is always a simple operation that returns a resource.
 	if !m.IsSimple() || m.InputType == nil || m.ReturnsEmpty || m.OutputType.Resource == nil {

internal/sidekick/rust/templates/common/client_method_samples/client_method_sample.mustache

@@ -19,9 +19,10 @@ limitations under the License.
 /// # Example
 /// ```
 /// # use {{Service.Model.Codec.PackageNamespace}}::client::{{Service.Codec.Name}};
+/// use {{Service.Model.Codec.PackageNamespace}}::Result;
 /// async fn sample(
 {{> /templates/common/client_method_samples/parameters}}
-/// ) -> gax::Result<()> {
+/// ) -> Result<()> {
 {{#ReturnsEmpty}}
 ///     client
 ///         .{{Codec.Name}}()