Remove unnecessary deprecate.h includes

[tautschnig]

The procedures or methods marked DEPRECATED have been removed already,
but the #include was unnecessarily left in place.

• 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

Merging #5567 (437b081) into develop (ff1e81e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #5567   +/-   ##
========================================
  Coverage    69.01%   69.01%           
========================================
  Files         1187     1187           
  Lines        98257    98257           
========================================
  Hits         67809    67809           
  Misses       30448    30448           

Flag	Coverage Δ
cproversmt2	43.09% <ø> (+<0.01%)	⬆️
regression	66.21% <ø> (ø)
unit	32.26% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/util/string_utils.h	100.00% <ø> (ø)
src/util/type.h	100.00% <ø> (ø)

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