[release-1.24] clarify ambient mode installation required for dns-proxy

[istio-testing]

Manual cherrypick required.

#16230 failed to apply on top of branch "release-1.24":

Applying: clarify ambient mode installation required for dns-proxy
Applying: presumptious changes
Using index info to reconstruct a base tree...
M	content/en/docs/ops/configuration/traffic-management/dns-proxy/index.md
M	content/en/docs/ops/configuration/traffic-management/dns-proxy/snips.sh
M	content/en/docs/ops/configuration/traffic-management/dns-proxy/test.sh
Falling back to patching base and 3-way merge...
Auto-merging content/en/docs/ops/configuration/traffic-management/dns-proxy/test.sh
CONFLICT (content): Merge conflict in content/en/docs/ops/configuration/traffic-management/dns-proxy/test.sh
Auto-merging content/en/docs/ops/configuration/traffic-management/dns-proxy/snips.sh
CONFLICT (content): Merge conflict in content/en/docs/ops/configuration/traffic-management/dns-proxy/snips.sh
Auto-merging content/en/docs/ops/configuration/traffic-management/dns-proxy/index.md
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"
Patch failed at 0002 presumptious changes