Remove stale temp.txt dev notes from repo root

temp.txt was an accidentally committed scratch note describing the
observite/react .d.ts type-duplication issue. That issue is already
resolved: src/observite-react.d.ts is hand-written to import types from
'observite', rollup copies it to lib/, and type-compatibility.test.ts
guards it (npm run test:types). The note is now obsolete clutter.

Author: durvesh1992