Turn notes into proper quoted blocks

docs/user/metrics/index.md

@@ -42,8 +42,4 @@ Labeled metrics come in two forms:
 - **Dynamic labels**: The labels aren't known at build time, so are set at run time.
   Only the first 16 labels seen by the Glean SDK will be tracked. After that, any additional labels are converted to the special label `__other__`.
 
----
-
-_Note:_ Be careful with using arbitrary strings as labels and make sure they can't accidentally contain identifying data (like directory paths or user input).
-
----
+> **Note**: Be careful with using arbitrary strings as labels and make sure they can't accidentally contain identifying data (like directory paths or user input).

docs/user/metrics/string.md

@@ -2,15 +2,9 @@
 
 This allows recording a Unicode string value with arbitrary content.
 
----
+> **Note**: Be careful using arbitrary strings and make sure they can't accidentally contain identifying data (like directory paths or user input).
 
-_Note:_ Be careful using arbitrary strings and make sure they can't accidentally contain identifying data (like directory paths or user input).
-
----
-
-_Note:_ This is does not support recording JSON blobs - please get in contact with the Telemetry team if you're missing a type.
-
----
+> **Note**: This is does not support recording JSON blobs - please get in contact with the Telemetry team if you're missing a type.
 
 ## Configuration