macOS regression: Drag and Drop seems to drop UTF-16 instead of UTF-8

Bug description:

In wxWidgets v3.3.3.1, Drag and Drop seems to be dropping plain text as UTF-16LE when UTF-8 would be appropriate. I could not reproduce this issue with v3.2.11.

Expected vs observed behaviour:

Use the dnd.app sample program and a suitable program to receive the drop, I suggest the terminal.app. Note that iTerm2 and some text editors will accept UTF-16 input and thereby mask the problem. Use the "File->Test Drag..." menu item to enter some test text, then drag it to the target window. Notice that the pasted text has a nul character after each character of the text. This does not happen with v3.2.11, the drop only pastes the plan text as expected. Normal copy/paste does not seem to be affected.

Patch or snippet allowing to reproduce the problem:

The standard dnd sample app is sufficient without modification.

To Reproduce:

1. Launch the dnd sample and the terminal app.
2. Use the "File->Test Drag..." menu item to enter some test text
3. Drag from the dnd window to the terminal window
4. Observe that UTF-16LE text is pasted into the terminal. This is the result of dragging the default text to the terminal prompt: w^@x^@W^@i^@d^@g^@e^@t^@s^@ ^@d^@r^@a^@g^@ ^@&^@ ^@d^@r^@o^@p^@ ^@w^@o^@r^@k^@s^@ ^@:^@-^@)^@ As a comparison 3.2.11 drops the text as: wxWidgets drag & drop works :-)

As an alternate test: Enter a URL as the test text and drag to the Safari URL bar, the text will be pasted thus: w%00x%00w%00i%00d%00g%00e%00t%00s%00.%00o%00r%00g%00

Platform and version information

• wxWidgets version you use: 3.3.3.1
• wxWidgets port you use: wxOSX
• OS and its version: macOS 15.7.9 on M1Max