Standardise casing of integration manager

Replace instances of 'Integration Manager' with 'Integration manager', when at start of
sentence, or 'integration manager' when not.

Signed-off-by: Paulo Pinto <paulo.pinto@automattic.com>

src/utils/WidgetUtils.ts

@@ -407,7 +407,7 @@ export default class WidgetUtils {
             "integration_manager_" + (new Date().getTime()),
             WidgetType.INTEGRATION_MANAGER,
             uiUrl,
-            "Integration Manager: " + name,
+            "Integration manager: " + name,
             { "api_url": apiUrl },
         );
     }