goto-harness: remove use of namespacet::follow

[tautschnig]

A pointer-typed expression cannot be of a tagged type, there is no need for follow/follow_tag here.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.66%. Comparing base (6cad8ca) to head (8761824).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8220      +/-   ##
===========================================
- Coverage    79.66%   79.66%   -0.01%     
===========================================
  Files         1682     1682              
  Lines       195371   195370       -1     
===========================================
- Hits        155642   155641       -1     
  Misses       39729    39729              

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