Update references to compositions in expression function help

resources/function_help/json/$map

@@ -1,9 +1,9 @@
 {
   "name": "$map",
   "type": "function",
-  "description": "Returns the id of the current map item if the map is being drawn in a composition, or \"canvas\" if the map is being drawn within the main QGIS window.",
+  "description": "Returns the id of the current map item if the map is being drawn in a print layout, or \"canvas\" if the map is being drawn within the main QGIS window.",
   "examples": [
-	{ "expression": "$map", "returns": "\"overview_map\"", "description": "within a composer item"},
+	{ "expression": "$map", "returns": "\"overview_map\"", "description": "within a layout map item"},
 	{ "expression": "$map", "returns": "\"canvas\"", "description": "within the main QGIS main canvas"}
   ]
 }

resources/function_help/json/$page

@@ -1,7 +1,7 @@
 {
   "name": "$page",
   "type": "function",
-  "description": "Returns the current page number within a composition.",
+  "description": "Returns the current page number within a print layout.",
   "examples": [ { "expression":"$page", "returns":"2"}
   ]
 }

resources/function_help/json/item_variables

@@ -2,8 +2,8 @@
   "name": "item_variables",
   "type": "function",
   "groups": ["Layout"],
-  "description": "Returns a map of variables from a composer item inside this composition.",
-  "arguments": [ {"arg":"id","description":"composer item ID"}],
+  "description": "Returns a map of variables from a layout item inside this print layout.",
+  "arguments": [ {"arg":"id","description":"layout item ID"}],
   "examples": [ { "expression":"map_get( item_variables('Map 0'), 'map_scale')", "returns":"scale of the item 'Map 0' in the current print layout"}
   ]
 }