clean: remove outdated microbundle cache directories

- microbundle hasn't used these directories in 3+ years
  - developit/microbundle@d0e66da
- and rollup-plugin-typescript2, which microbundle depends on and which
  actually created the dirs, hasn't used them in ~3 years either
  - ezolenko/rollup-plugin-typescript2@ffda2e5

- I help maintain rpt2 and formerly solo-maintained TSDX for ~1.5 years,
  which, as a fork of microbundle, has similarly used those directories
  in the past until I changed them
  - jaredpalmer/tsdx@55c0d47

Author: agilgur5

Node.gitignore

@@ -57,12 +57,6 @@ web_modules/
 # Optional stylelint cache
 .stylelintcache
 
-# Microbundle cache
-.rpt2_cache/
-.rts2_cache_cjs/
-.rts2_cache_es/
-.rts2_cache_umd/
-
 # Optional REPL history
 .node_repl_history