BadUSB: Fix key combos main keys being case sensitive

[WillyJL]

What's new

• [FL-3962] BadUSB arbitrary key combinations #4156 added arbitrary key combinations but changed the parsing of the main key of the key combo from ducky_get_keycode() to ducky_get_keycode_by_name() + BADUSB_ASCII_TO_KEY()
• this works fine, but has the side effect of changing behavior slightly: BADUSB_ASCII_TO_KEY() will return a keycode with modifier included, such as BADUSB_ASCII_TO_KEY(bad_usb, 'Z') will return the equivalent of SHIFT z not just z
• this was noticed by a user, where CTRL-ALT Z was no longer pressing ctrl+alt+z, but instead ctrl+shift+alt+z
• on one hand, it is simple enough to change to CTRL-ALT z, but on the other it seems more appropriate to consider keycodes without modifiers while processing a key combination, as the user is expected to specify it with CTRL-SHIFT-ALT Z for example, so this PR changes to the latter behavior, as it is also how key combinations worked previously; automatically adding modifiers such as SHIFT z with BADUSB_ASCII_TO_KEY() is used in the STRING and related commands, where it is more appropriate

Verification

• make a script with CTRL-ALT Z or any other key combo including a capital main letter
• try on https://www.mechanical-keyboard.org/key-rollover-test/ for example
• it should press only ctrl+alt+z instead of ctrl+shift+alt+z

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix