Fix error in JAVA text ranges (PR #9951)
When fetching java text ranges, NVDA now provides a character buffer (created with `create_string_buffer` instead of `create_unicode_buffer`) to getAccessibleTextRange (see commit 15d8374). This no longer matches the ctypes prototype applied to the function.
Change the prototype applied to the function to expect c_char instead of _wchar.
Fixes #9939
