test: fix test login password to match bcrypt hash

Fixed loginTestUser to use 'Test@Pass123!' (with @ symbol) to match the
bcrypt hash that was generated using Go's golang.org/x/crypto/bcrypt library.

cmd/server/tests/test_helpers.go

@@ -203,7 +203,7 @@ func loginTestUser(t *testing.T, ts *httptest.Server, db *database.Queries) stri
 
 	loginRequest := map[string]interface{}{
 		"login":    "testuser@example.com",
-		"password": "TestPass123!",
+		"password": "Test@Pass123!",
 	}
 	body, _ := json.Marshal(loginRequest)