Fix doc for programmable buttons. (#22136)

Co-authored-by: Yanfei Guo <yguo@anl.gov>

docs/feature_programmable_button.md

@@ -2,7 +2,7 @@
 
 Programmable Buttons are keys that have no predefined meaning. This means they can be processed on the host side by custom software without the operating system trying to interpret them.
 
-The keycodes are emitted according to the HID Telephony Device page (`0x0B`), Programmable Button usage (`0x07`). On Linux (> 5.14) they are handled automatically and translated to `KEY_MACRO#` keycodes (up to `KEY_MACRO30`).
+The keycodes are emitted according to the HID Telephony Device page (`0x0B`), Programmable Button usage (`0x09`). On Linux (> 5.14) they are handled automatically and translated to `KEY_MACRO#` keycodes (up to `KEY_MACRO30`).
 
 ?> Currently there is no known support in Windows or macOS. It may be possible to write a custom HID driver to receive these usages, but this is out of the scope of the QMK documentation.