Remove unused outdated help files

resources/function_help/json/$map

@@ -1,15 +0,0 @@
-{
-  "name": "$map",
-  "type": "function",
-  "description": "Returns the id of the current map item if the map is being drawn in a print layout, or \"canvas\" if the map is being drawn within the main QGIS window.",
-  "examples": [{
-    "expression": "$map",
-    "returns": "\"overview_map\"",
-    "description": "within a layout map item"
-  }, {
-    "expression": "$map",
-    "returns": "\"canvas\"",
-    "description": "within the main QGIS main canvas"
-  }],
-  "tags": ["layout", "item", "drawn", "current", "main", "print", "map", "window", "overview", "canvas"]
-}

resources/function_help/json/$page

@@ -1,10 +0,0 @@
-{
-  "name": "$page",
-  "type": "function",
-  "description": "Returns the current page number within a print layout.",
-  "examples": [{
-    "expression": "$page",
-    "returns": "2"
-  }],
-  "tags": ["layout", "print", "page", "current"]
-}

resources/function_help/json/$rownum

@@ -1,10 +0,0 @@
-{
-  "name": "$rownum",
-  "type": "function",
-  "description": "Returns the number of the current row.",
-  "examples": [{
-    "expression": "$rownum",
-    "returns": "4711"
-  }],
-  "tags": ["row", "number", "current"]
-}