clean: remove outdated `microbundle` cache directories

[agilgur5]

Summary

Remove outdated directories for microbundle from the Node gitignore

Details

Reasons for making this change:

• microbundle hasn't used these directories in 3+ years
• and rollup-plugin-typescript2, which microbundle depends on and which actually created the dirs, hasn't used them in ~3 years either
• 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

Noticed these when I used the built-in gitignore template in https://github.com/agilgur5/tsconfig/commit/8be4fdd46b578c20b6e173169bf8f51d25cd44a2

Links to documentation supporting these rule changes:

• https://github.com/developit/microbundle/pull/361
• https://github.com/ezolenko/rollup-plugin-typescript2/pull/167
• https://github.com/jaredpalmer/tsdx/pull/329