refactor: don't display anonymous lua functions

I find that showing anonymous functions is never helpful. These are
typically passed in as callback arguments to other functions, and are
not helpful to show in a symbol tree. They also break my expectations
for navigation.

queries/lua/aerial.scm

@@ -44,7 +44,3 @@
     (function_definition) @type)
   (#set! "kind" "Function")
 ) @start
-
-(function_definition
-  (#set! "kind" "Function")
-  ) @type

tests/treesitter/lua_spec.lua

@@ -38,17 +38,6 @@ describe("treesitter lua", function()
         col = 0,
         end_lnum = 18,
         end_col = 3,
-        children = {
-          {
-            kind = "Function",
-            name = "<Anonymous>",
-            level = 1,
-            lnum = 14,
-            col = 7,
-            end_lnum = 16,
-            end_col = 5,
-          },
-        },
       },
       {
         kind = "Function",