Deprecate `blob` in Snippet GraphQL type

It has been replaced by `blobs`

app/graphql/types/snippet_type.rb

@@ -66,7 +66,8 @@ module Types
     field :blob, type: Types::Snippets::BlobType,
           description: 'Snippet blob',
           calls_gitaly: true,
-          null: false
+          null: false,
+          deprecated: { reason: 'Use `blobs`', milestone: '13.3' }
 
     field :blobs, type: [Types::Snippets::BlobType],
           description: 'Snippet blobs',

changelogs/unreleased/vij-deprecate-graphql-snippet-blob.yml

+---
+title: Deprecate blob field on GraphQL SnippetType
+merge_request: 39088
+author:
+type: deprecated

doc/api/graphql/reference/gitlab_schema.graphql

@@ -13673,9 +13673,9 @@ type Snippet implements Noteable {
   author: User
 
   """
-  Snippet blob
+  Snippet blob. Deprecated in 13.3: Use `blobs`
   """
-  blob: SnippetBlob!
+  blob: SnippetBlob! @deprecated(reason: "Use `blobs`. Deprecated in 13.3")
 
   """
   Snippet blobs

doc/api/graphql/reference/gitlab_schema.json

@@ -40253,7 +40253,7 @@
             },
             {
               "name": "blob",
-              "description": "Snippet blob",
+              "description": "Snippet blob. Deprecated in 13.3: Use `blobs`",
               "args": [
 
               ],
@@ -40266,8 +40266,8 @@
                   "ofType": null
                 }
               },
-              "isDeprecated": false,
-              "deprecationReason": null
+              "isDeprecated": true,
+              "deprecationReason": "Use `blobs`. Deprecated in 13.3"
             },
             {
               "name": "blobs",

doc/api/graphql/reference/index.md

@@ -2020,7 +2020,7 @@ Represents a snippet entry
 | Name  | Type  | Description |
 | ---   |  ---- | ----------  |
 | `author` | User | The owner of the snippet |
-| `blob` | SnippetBlob! | Snippet blob |
+| `blob` **{warning-solid}** | SnippetBlob! | **Deprecated:** Use `blobs`. Deprecated in 13.3 |
 | `blobs` | SnippetBlob! => Array | Snippet blobs |
 | `createdAt` | Time! | Timestamp this snippet was created |
 | `description` | String | Description of the snippet |