Update immediategeometry.rst

"
.......
moudules/gdscript/gdscript_tokenizer.cpp:1104 - Condition ' tk_rb[ofs].type != TK_IDENTIFER ' is true. returned: StringName()"
built-in:3 - Parse Error: Unexpected token: void:
modules/gdscript/gdscript.cpp:580 - Method/Function Faild, returning: ERR_PARSE_ERROR
moudules/gdscript/gdscript_tokenizer.cpp:1104 - Condition ' tk_rb[ofs].type != TK_IDENTIFER ' is true. returned: StringName()
.......
"

tutorials/content/procedural_geometry/immediategeometry.rst

@@ -42,7 +42,7 @@ The example code below draws a single triangle.
 
     extends ImmediateGeometry
 
-    void _process(delta):
+    func _process(delta):
         # Clean up before drawing.
         clear()