[template/text] Fix lambda config (#6655)

Co-authored-by: Clyde Stubbs <2366188+clydebarrow@users.noreply.github.com>

tests/component_tests/text/test_text.yaml

@@ -31,3 +31,15 @@ text:
     optimistic: true
     internal: true
     max_length: 255
+
+  - platform: template
+    name: "test 4 key"
+    id: "it_4"
+    mode: text
+    set_action:
+      - then:
+          - logger.log:
+              format: Template text set to %s
+              args: ["x.c_str()"]
+    lambda: |
+      return std::string{"Hello"};