fixing prob. /w symbol/ string correspondence

[Mytolo]

PR Checklist

• Update NEWS.md?
• Unit tests for all structs / functions?
• Integration and correctness tests using a simple env?
• PR Review?
• Add or update documentation?
• Write docstrings for new methods?

PettingZoo environments had problems with agent identification symbol to string conversion. Was just a minor bug after readjusting the wrapper here.

[codecov]

Codecov Report

Merging #934 (1431a78) into main (1f7f347) will decrease coverage by 13.65%.
The diff coverage is 0.00%.

❗ Current head 1431a78 differs from pull request most recent head 5d951b1. Consider uploading reports for the commit 5d951b1 to get more accurate results

@@            Coverage Diff             @@
##             main    #934       +/-   ##
==========================================
- Coverage   13.64%   0.00%   -13.65%     
==========================================
  Files         217     208        -9     
  Lines        7571    7410      -161     
==========================================
- Hits         1033       0     -1033     
- Misses       6538    7410      +872     

Files Changed	Coverage Δ
...ironments/src/environments/3rd_party/pettingzoo.jl	0.00% <0.00%> (ø)

... and 42 files with indirect coverage changes