Fix tape printing

[gdalle]

Fixes EnzymeAD/Enzyme.jl#1354

[devmotion]

Can you add a test (eg using string or an IOBuffer?)?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 81.47%. Comparing base (c982cde) to head (d1fc4b6).
Report is 1 commits behind head on master.

❗ Current head d1fc4b6 differs from pull request most recent head f5ce5fb. Consider uploading reports for the commit f5ce5fb to get more accurate results

Files	Patch %	Lines
src/tape.jl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #252      +/-   ##
==========================================
- Coverage   81.53%   81.47%   -0.07%     
==========================================
  Files          18       18              
  Lines        1587     1576      -11     
==========================================
- Hits         1294     1284      -10     
+ Misses        293      292       -1     

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[gdalle]

Can you add a test (eg using string or an IOBuffer?)?

done

[devmotion]

Looks good to me, thanks!