Change field descriptions for singular 'label' fields

This corrects the descriptions for singular 'label' fields

app/graphql/types/group_type.rb

@@ -69,7 +69,7 @@ module Types
     field :label,
           Types::LabelType,
           null: true,
-          description: 'Labels available on this group' do
+          description: 'A label available on this group' do
             argument :title, GraphQL::STRING_TYPE,
               required: true,
               description: 'The title of the label'

app/graphql/types/project_type.rb

@@ -246,7 +246,7 @@ module Types
     field :label,
           Types::LabelType,
           null: true,
-          description: 'Labels available on this project' do
+          description: 'A label available on this project' do
             argument :title, GraphQL::STRING_TYPE,
               required: true,
               description: 'The title of the label'

doc/api/graphql/reference/gitlab_schema.graphql

@@ -4653,7 +4653,7 @@ type Group {
   ): IterationConnection
 
   """
-  Labels available on this group
+  A label available on this group
   """
   label(
     """
@@ -8404,7 +8404,7 @@ type Project {
   jobsEnabled: Boolean
 
   """
-  Labels available on this project
+  A label available on this project
   """
   label(
     """

doc/api/graphql/reference/gitlab_schema.json

@@ -12822,7 +12822,7 @@
             },
             {
               "name": "label",
-              "description": "Labels available on this group",
+              "description": "A label available on this group",
               "args": [
                 {
                   "name": "title",
@@ -24724,7 +24724,7 @@
             },
             {
               "name": "label",
-              "description": "Labels available on this project",
+              "description": "A label available on this project",
               "args": [
                 {
                   "name": "title",

doc/api/graphql/reference/index.md

@@ -706,7 +706,7 @@ Autogenerated return type of EpicTreeReorder
 | `fullPath` | ID! | Full path of the namespace |
 | `groupTimelogsEnabled` | Boolean | Indicates if Group timelogs are enabled for namespace |
 | `id` | ID! | ID of the namespace |
-| `label` | Label | Labels available on this group |
+| `label` | Label | A label available on this group |
 | `lfsEnabled` | Boolean | Indicates if Large File Storage (LFS) is enabled for namespace |
 | `mentionsDisabled` | Boolean | Indicates if a group is disabled from getting mentioned |
 | `name` | String! | Name of the namespace |
@@ -1220,7 +1220,7 @@ Information about pagination in a connection.
 | `issuesEnabled` | Boolean | Indicates if Issues are enabled for the current user |
 | `jiraImportStatus` | String | Status of Jira import background job of the project |
 | `jobsEnabled` | Boolean | Indicates if CI/CD pipeline jobs are enabled for the current user |
-| `label` | Label | Labels available on this project |
+| `label` | Label | A label available on this project |
 | `lastActivityAt` | Time | Timestamp of the project last activity |
 | `lfsEnabled` | Boolean | Indicates if the project has Large File Storage (LFS) enabled |
 | `mergeRequest` | MergeRequest | A single merge request of the project |