test: Remove references to tiny.vim/small.vim/mbyte.vim

Vim creates these scripts in test1 depending on what build features
are enabled so that tests that use these features are skiped if
necessary. Because Neovim only has one type of build (and the features
+eval, +windows, and +multi-byte are enabled in this build) they are
not necessary.

test/benchmark/bench_re_freeze_spec.lua

@@ -25,8 +25,8 @@ local measure_script = [[
     endfunc]]
 
 describe('regexp search', function()
-  -- The test cases rely on a small Vim script, which we source here, and also
-  -- on a temporary result file, which we prepare and write to disk.
+  -- The test cases rely on a temporary result file, which we prepare and write
+  -- to disk.
   setup(function()
     clear()
     source(measure_script)