Remove bump_version from transit import docs (hashicorp#21393)

- The argument was removed along the development path, but the
   documentation was not updated.

website/content/api-docs/secret/transit.mdx

@@ -253,12 +253,9 @@ imported. This limits the operations available under this key to verification
 and encryption, depending on the key type and algorithm, as no private key
 is available.
 
-- `bump_version` - By default, each operator will create a new key version.
-If set to "false", will try to update the latest version of the key,
-unless changed in parameter `version`.
-
-- `version` - Key version to be updated, if left empty "Latest" version will be updated.
-If `bump_version` is set to "true", this field is ignored.
+- `version` `(int, optional)` - Key version to be updated, if left empty,
+a new version will be created unless a private key is specified and the
+'Latest' key is missing a private key.
 
 ### Sample Payload