Fix on warning structure content in introduction

docs/introduction-to-smart-contracts.rst

@@ -616,8 +616,8 @@ but you can reasonably expect them to always be in the range between
 ``1`` and ``0xffff`` (inclusive).
 
 .. warning::
-Since the 0.8.10 release the compiler does not check ``extcodesize`` on external calls if return data is expected,
-since an empty code will be unable to return data, and the ABI decoder will revert.
-This is an exception for external calls over precompiled contracts which are able to return data without code associated with their addresses.
+    Since the 0.8.10 release the compiler does not check ``extcodesize`` on external calls if return data is expected,
+    since an empty code will be unable to return data, and the ABI decoder will revert.
+    This is an exception for external calls over precompiled contracts which are able to return data without code associated with their addresses.
 
-    More on  :ref:`external function calls <external-function-calls>` and :ref:`low-level calls <address_related>`.
+    More on  :ref:`external function calls <external-function-calls>` and :ref:`low-level calls <address_related>`.