Backport: fix(bedrock): skip passing unsigned reasoning content

[github-actions]

This is an automated backport of #15181 to the release-v6.0 branch. FYI @aayush-kapoor
This backport has conflicts that need to be resolved manually.

git cherry-pick output

Auto-merging packages/amazon-bedrock/src/convert-to-bedrock-chat-messages.test.ts
CONFLICT (content): Merge conflict in packages/amazon-bedrock/src/convert-to-bedrock-chat-messages.test.ts
Auto-merging packages/amazon-bedrock/src/convert-to-bedrock-chat-messages.ts
CONFLICT (content): Merge conflict in packages/amazon-bedrock/src/convert-to-bedrock-chat-messages.ts
error: could not apply bcbaae644... fix(bedrock): skip passing unsigned reasoning content (#15181)
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".
hint: Disable this message with "git config set advice.mergeConflict false"

[github-actions]

🚀 Published in:

Package	Version
@ai-sdk/amazon-bedrock	4.0.104