Update interpolation.html.md

Small changes to case on interpolation syntaxes, dealing with case.

website/source/docs/configuration/interpolation.html.md

@@ -154,7 +154,7 @@ The supported built-in functions are:
       variable. The `map` parameter should be another variable, such
       as `var.amis`.
 
-  * `lower(string)` - returns a copy of the string with all Unicode letters mapped to their lower case.
+  * `lower(string)` - Returns a copy of the string with all Unicode letters mapped to their lower case.
 
   * `replace(string, search, replace)` - Does a search and replace on the
       given string. All instances of `search` are replaced with the value
@@ -172,7 +172,7 @@ The supported built-in functions are:
       `a_resource_param = ["${split(",", var.CSV_STRING)}"]`.
       Example: `split(",", module.amod.server_ids)`
 
-  * `upper(string)` - returns a copy of the string with all Unicode letters mapped to their upper case.
+  * `upper(string)` - Returns a copy of the string with all Unicode letters mapped to their upper case.
 
 ## Templates