doc(api): Default value for `delete_ring_tokens` on `/ingester/shutdown` endpoint (#7921)

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

**What this PR does / why we need it**:
PR documents the default value for `delete_ring_tokens` params on
`/ingester/shutdown` endpoint.

**Which issue(s) this PR fixes**:
Fixes #NA

**Special notes for your reviewer**:

**Checklist**
- [x] Documentation added

Signed-off-by: Kaviraj <kavirajkanagaraj@gmail.com>

docs/sources/api/_index.md

@@ -637,7 +637,7 @@ It accepts three URL query parameters `flush`, `delete_ring_tokens`, and `termin
 * `flush=<bool>`:
   Flag to control whether to flush any in-memory chunks the ingester holds. Defaults to `true`.
 * `delete_ring_tokens=<bool>`:
-  Flag to control whether to delete the file that contains the ingester ring tokens of the instance if the `-ingester.token-file-path` is specified.
+  Flag to control whether to delete the file that contains the ingester ring tokens of the instance if the `-ingester.token-file-path` is specified. Defaults to `false.
 * `terminate=<bool>`:
   Flag to control whether to terminate the Loki process after service shutdown. Defaults to `true`.
 
@@ -1385,4 +1385,3 @@ This is helpful for scaling down WAL-enabled ingesters where we want to ensure o
 but instead flushed to our chunk backend.
 
 In microservices mode, the `/ingester/flush_shutdown` endpoint is exposed by the ingester.
-