fix(ibc): prevent arbitrary src_callback execution

[mmsqe]

Description

Closes: #XXXX

---

Author Checklist

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please add links to any relevant follow up issues.

I have...

• tackled an existing issue or discussed with a team member
• left instructions on how to review the changes
• targeted the main branch

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.60%. Comparing base (c0d34cb) to head (f3fd925).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #993      +/-   ##
==========================================
+ Coverage   65.47%   65.60%   +0.12%     
==========================================
  Files         319      319              
  Lines       22224    22194      -30     
==========================================
+ Hits        14552    14560       +8     
+ Misses       6492     6485       -7     
+ Partials     1180     1149      -31     

Files with missing lines	Coverage Δ
x/ibc/callbacks/keeper/keeper.go	58.99% <100.00%> (-11.38%)	⬇️

... and 3 files with indirect coverage changes

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[vladjdk]

Lgtm - could we get a quick description in an issue attached to the PR before we merge?