Unnecessary verification

[ashm-tech]

Describe the bug
While searching for a vulnerability error in sqlparse, I found one assert that does not affect (in my opinion) anything, because if you comment it and run tests, they pass without errors and also the example code also pass without errors
Here is the link to the code:

sqlparse/sqlparse/sql.py

Line 236 in 3696d53

assert end is None

To Reproduce
In order to check this, comment out this line and run the tests in any way (with the tox or pytest command) and see that the tests are being passed

Expected behavior
If this check would have made sense then at least one test should have fallen)

Versions (please complete the following information):

• Python: [e.g. 3.11.5]
• sqlparse: [e.g. 0.5.0.dev0]

Additional context
If this check still turns out to be necessary, it is better to get rid of the asserts in the code (assert is performed only in debug mode or in tests) and add an if condition. I can send a PR with an update