Fix test:typescript script for Windows compatibility #5928

PS C:\Users\shivams\Desktop\open-source\undici> npm run test:typescript
npm notice run undici@8.11.2 test:typescript
npm notice run tsd && tsc test/imports/undici-import.ts --typeRoots ./types --noEmit && tsc ./types/*.d.ts --noEmit --typeRoots ./types
error TS6053: File './types/*.d.ts' not found.
  The file is in the program because:
    Root file specified for compilation

Found 1 error.