Fix check-deps.sh to check for weak symbols so it can detect when an exported
template function is used from another library.
In a previous version of this commit, this change caused an invalid dependency
in the consensus library on the TryParseHex template function from the util
library to be detected, and a suppression was added here. But #30377 removed
the invalid dependency so the suppression is no longer needed.
The invalid dependency and problem detecting weak symbol usage was originally
reported by Hennadii Stepanov in
https://github.com/bitcoin/bitcoin/pull/29015#issuecomment-2209258843
