fix/users: remove query for usageStatistics (#1264)

This field was deprecated in March last year and was removed November
last year. Before this change any user subcommand just failed. Will be
adding some integration smoke tests to catch these sort of issues.

Additionally found one place we didn't set Content-Type which
Sourcegraph also recently started enforcing.

Author: keegancsmith

cmd/src/users.go

@@ -60,10 +60,6 @@ fragment UserFields on User {
         email
 		verified
     }
-    usageStatistics {
-        lastActiveTime
-        lastActiveCodeHostIntegrationTime
-    }
     url
 }
 `
@@ -76,21 +72,15 @@ type User struct {
 	Organizations struct {
 		Nodes []Org
 	}
-	Emails          []UserEmail
-	UsageStatistics UserUsageStatistics
-	URL             string
+	Emails []UserEmail
+	URL    string
 }
 
 type UserEmail struct {
 	Email    string
 	Verified bool
 }
 
-type UserUsageStatistics struct {
-	LastActiveTime                    string
-	LastActiveCodeHostIntegrationTime string
-}
-
 type SiteUser struct {
 	ID           string
 	Username     string

internal/users/admin.go

@@ -252,6 +252,7 @@ func (c *Client) GraphQL(token, query string, variables map[string]any, target a
 	if err != nil {
 		return err
 	}
+	req.Header.Set("Content-Type", "application/json")
 	if token != "" {
 		req.Header.Set("Authorization", fmt.Sprintf("token %s", token))
 	} else {