Docs: Update template variable overview to contain the preferred variable syntax (#25176)

* Update templates-and-variables.md

Fixes #13744

* Update templates-and-variables.md

* Update templates-and-variables.md

* Update docs/sources/variables/templates-and-variables.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/variables/templates-and-variables.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update docs/sources/variables/templates-and-variables.md

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

docs/sources/variables/templates-and-variables.md

@@ -43,9 +43,9 @@ Panel titles and metric queries can refer to variables using two different synta
 - `$varname`
   This syntax is easy to read, but it does not allow you to use a variable in the middle of a word.
   **Example:** apps.frontend.$server.requests.count
-- `[[varname]]` 
-  **Note:** This syntax might be deprecated in the future.
-  Example: apps.frontend.[[server]].requests.count
+- `${var_name}` Use this syntax when you want to interpolate a variable in the middle of an expression. 
+- `${var_name:<format>}` This format gives you more control over how Grafana interpolates values. Refer to [Advanced variable format options]({{< relref "advanced-variable-format-options.md" >}}) for more detail on all the formatting types.
+- `[[varname]]` Do not use. Deprecated old syntax, will be removed in a future release. 
 
 Before queries are sent to your data source the query is _interpolated_, meaning the variable is replaced with its current value. During
 interpolation, the variable value might be _escaped_ in order to conform to the syntax of the query language and where it is used.