X-Chain API doc fix (#3654)

Signed-off-by: Meaghan FitzGerald <meag.fitz@avalabs.org>

Author: meaghanfitzgerald

vms/avm/service.md

@@ -233,10 +233,6 @@ curl -X POST --data '{
 }
 ```
 
-<!--
-TODO: Add avm.createAsset
--->
-
 ### `avm.createFixedCapAsset`
 
 :::caution
@@ -597,10 +593,6 @@ curl -X POST --data '{
 }
 ```
 
-<!--
-TODO: Add avm.exportAVAX
--->
-
 ### `avm.exportKey`
 
 :::caution
@@ -1491,10 +1483,6 @@ curl -X POST --data '{
 }
 ```
 
-<!--
-TODO: Add avm.importAVAX
--->
-
 ### `avm.importKey`
 
 :::caution