Fix: release alpn string before set for tls_ctx_options

[xiazhvera]

Issue #, if available:

Description of changes:

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[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (f7bc831) 79.94% compared to head (13fe790) 79.94%.

❗ Current head 13fe790 differs from pull request most recent head 12779df. Consider uploading reports for the commit 12779df to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #588   +/-   ##
=======================================
  Coverage   79.94%   79.94%           
=======================================
  Files          27       27           
  Lines        5844     5845    +1     
=======================================
+ Hits         4672     4673    +1     
  Misses       1172     1172           

Files Changed	Coverage Δ
source/tls_channel_handler.c	62.96% <100.00%> (+0.15%)	⬆️

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