Use type_try_dynamic_cast in particular case where it clarifies the code

[NathanJPhillips]

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• 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).
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[codecov-io]

Codecov Report

Merging #5088 into develop will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           develop    #5088   +/-   ##
========================================
  Coverage    69.66%   69.66%           
========================================
  Files         1319     1319           
  Lines       109234   109234           
========================================
  Hits         76102    76102           
  Misses       33132    33132

Impacted Files	Coverage Δ
jbmc/src/java_bytecode/java_types.cpp	96.74% <100%> (ø)	⬆️

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[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 35fb893).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/126036077