Update playbooks_blocks.rst (#40951)

Blocks currently don't support loops such as with_items or sequence.  It would be helpful to make this clear in the docs otherwise it's a bit of a gotcha.

+label: docsite_pr

docs/docsite/rst/user_guide/playbooks_blocks.rst

@@ -1,7 +1,7 @@
 Blocks
 ======
 
-Blocks allow for logical grouping of tasks and in play error handling. Most of what you can apply to a single task can be applied at the block level, which also makes it much easier to set data or directives common to the tasks. This does not mean the directive affects the block itself, but is inherited by the tasks enclosed by a block. i.e. a `when` will be applied to the tasks, not the block itself.
+Blocks allow for logical grouping of tasks and in play error handling. Most of what you can apply to a single task (with the exception of loops) can be applied at the block level, which also makes it much easier to set data or directives common to the tasks. This does not mean the directive affects the block itself, but is inherited by the tasks enclosed by a block. i.e. a `when` will be applied to the tasks, not the block itself.
 
 
 .. code-block:: YAML