vfs: fix RealFSProvider watchFile listener

[Y1D7NG]

Fixes: #64536

RealFSProvider.watchFile ignored the listener, so changes never reached code.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.24%. Comparing base (7a11a9b) to head (7e9e436).
⚠️ Report is 12 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #64537 +/- ##
=======================================
Coverage 90.24% 90.24% =======================================
Files 739 739 Lines 241669 241668 -1 Branches 45543 45546 +3 =======================================
+ Hits 218087 218099 +12 + Misses 15150 15108 -42 - Partials 8432 8461 +29 

Files with missing lines	Coverage Δ
lib/internal/vfs/provider.js	98.38% <100.00%> (+<0.01%)	⬆️
lib/internal/vfs/providers/real.js	96.07% <100.00%> (ø)

... and 46 files with indirect coverage changes

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