Fix position info for equality expr errors

[FliegendeWurst]

Intended Change

This PR fixes the position info of the error for incorrect equality expressions.

Type of pull request

• Bug fix (non-breaking change which fixes an issue)
• Refactoring (behaviour should not change or only minimally change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• There are changes to the (Java) code
• There are changes to the taclet rule base
• There are changes to the deployment/CI infrastructure (gradle, github, ...)
• Other:

Ensuring quality

• I made sure that introduced/changed code is well documented (javadoc and inline comments).
• I made sure that new/changed end-user features are well documented (https://github.com/KeYProject/key-docs).
• I added new test case(s) for new functionality: I re-enabled the test case by no longer marking it as broken
• I have tested the feature as follows: automated test
• I have checked that runtime performance has not deteriorated.

Additional information and contact(s)

The contributions within this pull request are licensed under GPLv2 (only) for inclusion in KeY.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1fb0c10) 37.77% compared to head (0e66dd9) 37.77%.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #3429   +/-   ##
=========================================
  Coverage     37.77%   37.77%           
- Complexity    17031    17036    +5     
=========================================
  Files          2076     2076           
  Lines        126950   126951    +1     
  Branches      21381    21381           
=========================================
+ Hits          47952    47962   +10     
+ Misses        73092    73084    -8     
+ Partials       5906     5905    -1     

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