gcloud-kms-decrypt: add page. (#11689)

* I have added gcloud-components_update.

* gcloud-kms-decrypt: new page

* deleted pages/common/gcloud-components_update: empty page

* gcloud-kms-decrypt: suggestions fix

* gcloud-kms-decrypt: suggestions fix

pages/common/gcloud-kms-decrypt.md

@@ -0,0 +1,13 @@
+# gcloud kms decrypt
+
+> Decrypt a ciphertext file using a Cloud KMS key.
+> See also: `gcloud`.
+> More information: <https://cloud.google.com/sdk/gcloud/reference/kms/decrypt>.
+
+- Decrypt a file using a specified key, key ring, and location:
+
+`gcloud kms decrypt --key={{key_name}} --keyring={{keyring_name}} --location={{global}} --ciphertext-file={{path/to/ciphertext}} --plaintext-file={{path/to/plaintext}}`
+
+- Decrypt a file with additional authenticated data (AAD) and write the decrypted plaintext to `stdout`:
+
+`gcloud kms decrypt --key={{key_name}} --keyring={{keyring_name}} --location={{global}} --additional-authenticated-data-file={{path/to/file.aad}} --ciphertext-file={{path/to/ciphertext}} --plaintext-file=-`