Update limits.mdx

Author: thomasgauvin

src/content/docs/kv/platform/limits.mdx

@@ -23,6 +23,7 @@ import { Render } from "~/components"
 | Key size                     | 512 bytes             | 512 bytes    |
 | Key metadata                 | 1024 bytes            | 1024 bytes   |
 | Value size                   | 25 MiB                | 25 MiB       |
+| Minimum time-to-live         | 60 seconds            | 60 seconds   |