Fix RST formatting for --warn-unreachable example

Author: brovoski69

docs/source/command_line.rst

@@ -537,13 +537,15 @@ potentially problematic or redundant in some way.
                 print(x + "bad")
     Note that unreachable ``pass`` statements are intentionally not
     reported by this option. This allows ``pass`` to be used as a
-    placeholder during development without triggering an error.For
-    example::
+    placeholder during development without triggering an error.
+
+    For example::
+
+    def f(x: int) -> None:
+        if x > 0:
+            return
+            pass  # no --warn-unreachable error is reported here
 
-       def f(x: int) -> None:
-           if x > 0:
-               return
-               pass  # no --warn-unreachable error is reported here
 
     To help prevent mypy from generating spurious warnings, the "Statement is
     unreachable" warning will be silenced in exactly two cases: