feat: add deferred installation wording to validation installation (#165)

Author: fangting-alchemy

standard/ERCs/erc-6900.md

@@ -466,9 +466,10 @@ TODO for v0.8
 
 #### Validations and their installation /uninstallation
 
-An account can have more than one validation installed.
+An account can have more than one validation module/function installed.
 An account can have the same validation module installed more than once.
-The entityId of a validation installed on an account MUST be unique.
+The entityId of a validation function installed on an account MUST be unique.
+Validation installation MAY be deferred until a later time, such as upon first use.
 
 #### Responsibilties of `StandardExecutor` and `ModuleExecutor`