genpolicy: ignore volume configMap optional field

The auto-generated Policy already allows these volumes to be mounted,
regardless if they are:
- Present, or
- Missing and optional

Fixes: #8893

Signed-off-by: Dan Mihai <dmihai@microsoft.com>

src/tools/genpolicy/src/volume.rs

@@ -71,6 +71,7 @@ pub struct PersistentVolumeClaimVolumeSource {
 pub struct ConfigMapVolumeSource {
     pub name: String,
     pub items: Option<Vec<KeyToPath>>,
+    optional: Option<bool>,
     // TODO: additional fields.
 }