Rename $finishHandler to $finalHandler for consistency

[vjik]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	✔️
Tests pass?	✔️

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.50%. Comparing base (8937f11) to head (1619962).

Files with missing lines	Patch %	Lines
src/Middleware/Push/PushMiddlewareDispatcher.php	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #333   +/-   ##
=========================================
  Coverage     92.50%   92.50%           
  Complexity      383      383           
=========================================
  Files            59       59           
  Lines          1014     1014           
=========================================
  Hits            938      938           
  Misses           76       76           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.