[release-1.23] edited base64 decode command

[istio-testing]

Manual cherrypick required.

#15691 failed to apply on top of branch "release-1.23":

Applying: edited base64 decode command
Applying: make gen changes
Using index info to reconstruct a base tree...
M	content/en/docs/tasks/security/authorization/authz-jwt/snips.sh
Falling back to patching base and 3-way merge...
Auto-merging content/en/docs/tasks/security/authorization/authz-jwt/snips.sh
CONFLICT (content): Merge conflict in content/en/docs/tasks/security/authorization/authz-jwt/snips.sh
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0002 make gen changes
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".