cprover: Replace uses of namespacet::follow

[tautschnig]

This is deprecated. Use suitable variants of follow_tag instead.

• 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

Attention: Patch coverage is 37.50000% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 79.67%. Comparing base (6cad8ca) to head (e81bda6).

Files	Patch %	Lines
src/cprover/bv_pointers_wide.cpp	37.50%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8219   +/-   ##
========================================
  Coverage    79.66%   79.67%           
========================================
  Files         1682     1682           
  Lines       195371   195372    +1     
========================================
+ Hits        155642   155658   +16     
+ Misses       39729    39714   -15     

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