feat(gkebackup): update the api

#### gkebackup:v1

The following keys were added:
- schemas.BackupPlan.properties.rpoRiskLevel (Total Keys: 3)
- schemas.BackupPlan.properties.rpoRiskReason (Total Keys: 2)
- schemas.Date (Total Keys: 8)
- schemas.DayOfWeekList (Total Keys: 4)
- schemas.ExclusionWindow (Total Keys: 8)
- schemas.RpoConfig (Total Keys: 6)
- schemas.Schedule.properties.nextScheduledBackupTime (Total Keys: 3)
- schemas.Schedule.properties.rpoConfig.$ref (Total Keys: 1)
- schemas.TimeOfDay (Total Keys: 10)

docs/dyn/gkebackup_v1.projects.locations.backupPlans.backups.html

@@ -91,6 +91,9 @@ <h2>Instance Methods</h2>
 <p class="toc_element">
   <code><a href="#get">get(name, x__xgafv=None)</a></code></p>
 <p class="firstline">Retrieve the details of a single Backup.</p>
+<p class="toc_element">
+  <code><a href="#getBackupIndexDownloadUrl">getBackupIndexDownloadUrl(backup, x__xgafv=None)</a></code></p>
+<p class="firstline">Retrieve the link to the backupIndex.</p>
 <p class="toc_element">
   <code><a href="#getIamPolicy">getIamPolicy(resource, options_requestedPolicyVersion=None, x__xgafv=None)</a></code></p>
 <p class="firstline">Gets the access control policy for a resource. Returns an empty policy if the resource exists and does not have a policy set.</p>
@@ -312,6 +315,25 @@ <h3>Method Details</h3>
 }</pre>
 </div>
 
+<div class="method">
+    <code class="details" id="getBackupIndexDownloadUrl">getBackupIndexDownloadUrl(backup, x__xgafv=None)</code>
+  <pre>Retrieve the link to the backupIndex.
+
+Args:
+  backup: string, Required. Full name of Backup resource. Format: projects/{project}/locations/{location}/backupPlans/{backup_plan}/backups/{backup} (required)
+  x__xgafv: string, V1 error format.
+    Allowed values
+      1 - v1 error format
+      2 - v2 error format
+
+Returns:
+  An object of the form:
+
+    { # Response message for GetBackupIndexDownloadUrl.
+  &quot;signedUrl&quot;: &quot;A String&quot;,
+}</pre>
+</div>
+
 <div class="method">
     <code class="details" id="getIamPolicy">getIamPolicy(resource, options_requestedPolicyVersion=None, x__xgafv=None)</code>
   <pre>Gets the access control policy for a resource. Returns an empty policy if the resource exists and does not have a policy set.