Remove requireTransaction() and $isolationLevel from AbstractCommand

[vjik]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	✔️
Fix #782

Related PRs:

• Remove CommandTest::testExecuteWithTransaction db-oracle#337

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 99.00%. Comparing base (0d41aa8) to head (1f51f11).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Driver/Pdo/AbstractPdoCommand.php	87.50%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #999      +/-   ##
============================================
+ Coverage     98.91%   99.00%   +0.09%     
+ Complexity     1677     1673       -4     
============================================
  Files           102      102              
  Lines          4240     4228      -12     
============================================
- Hits           4194     4186       -8     
+ Misses           46       42       -4     

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