fix(docs): correct docs for CUSTOMER_MANAGED_ENCRYPTION (#737)

* fix(docs): correct docs for CUSTOMER_MANAGED_ENCRYPTION

* fix(docs): correct docs for CUSTOMER_MANAGED_ENCRYPTION

Author: kolea2

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/admin/v2/models/EncryptionInfo.java

@@ -32,13 +32,16 @@ public enum Type {
         com.google.bigtable.admin.v2.EncryptionInfo.EncryptionType.ENCRYPTION_TYPE_UNSPECIFIED),
     /**
      * The data backing this resource is encrypted at rest with a key that is fully managed by
-     * Google. No key version or status will be populated.
+     * Google. No key version or status will be populated. This is the default state.
      */
     GOOGLE_DEFAULT_ENCRYPTION(
         com.google.bigtable.admin.v2.EncryptionInfo.EncryptionType.GOOGLE_DEFAULT_ENCRYPTION),
     /**
-     * The data backing this resource is encrypted at rest with a key that is fully managed by
-     * Google. No key version or status will be populated. This is the default state.
+     * The data backing this resource is encrypted at rest with a key that is managed by the
+     * customer. The in-use version of the key and its status are populated for CMEK-protected
+     * tables. CMEK-protected backups are pinned to the key version that was in use at the time the
+     * backup was taken. This key version is populated but its status is not tracked and is reported
+     * as `UNKNOWN`.
      */
     CUSTOMER_MANAGED_ENCRYPTION(
         com.google.bigtable.admin.v2.EncryptionInfo.EncryptionType.CUSTOMER_MANAGED_ENCRYPTION),