Minor cluster coordination docs fixes (#42111)

Fixes a typo and a badly-formatted warning.

docs/reference/modules/discovery/discovery-settings.asciidoc

@@ -31,7 +31,7 @@ Discovery and cluster formation are also affected by the following
 _expert-level_ settings, although it is not recommended to change any of these
 from their default values.
 
-[WARNING] If you adjust these settings then your cluster may not form correctly
+WARNING: If you adjust these settings then your cluster may not form correctly
 or may become unstable or intolerant of certain failures.
 
 `discovery.cluster_formation_warning_timeout`::

docs/reference/setup/important-settings/heap-size.asciidoc

@@ -10,7 +10,7 @@ Elasticsearch will assign the entire heap specified in
 heap size) settings. You should set these two settings to be equal to each
 other.
 
-The value for these setting depends on the amount of RAM available on your
+The value for these settings depends on the amount of RAM available on your
 server:
 
 * Set `Xmx` and `Xms` to no more than 50% of your physical RAM. {es} requires