Fix: Support string input for $contents in Exception constructor

[sterzuccio]

What:

• [x] Bug Fix
• [ ] New Feature

Description:

Fix: Handle cases where $contents is a string instead of an array. Updated constructor to support both array and string types, preventing errors when $contents is not an array.

Related:

[iBotPeaches]

Marking as draft due to CI failures.

[iBotPeaches]

This was fixed in https://github.com/openai-php/client/pull/643 as it was refactored for object or string/object calls (to account for audio stringable responses). This shouldn't occur anymore since path of string returns won't have this possibility anymore.