test: add missing r.close() calls in REPL multiline tests

[Han5991]

Summary

• Adds missing r.close() calls to 4 test cases in test/parallel/test-repl-multiline-navigation.js
• Prevents resource leaks by properly cleaning up REPL instances after each test
• Ensures test isolation and improves reliability in CI environments

Test plan

• Run the modified test file: ./node test/parallel/test-repl-multiline-navigation.js
• Verify all tests pass without resource warnings
• Run full REPL test suite: tools/test.py repl
• Check for any memory leak indicators in test output

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.57%. Comparing base (f9fcc74) to head (57da92f).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #60226   +/-   ##
=======================================
  Coverage   88.56%   88.57%           
=======================================
  Files         704      704           
  Lines      208125   208125           
  Branches    40003    40009    +6     
=======================================
+ Hits       184332   184338    +6     
- Misses      15809    15815    +6     
+ Partials     7984     7972   -12     

see 24 files with indirect coverage changes

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