Use %p instead of %P for strftime (#1070)

## What are the changes about?
%P is a GNU extension and returns an empty string on musl, changed to %p
_Replace this with a brief description of your changes_
literally just "sed -i '1964s/"%P"/"%p"/' src/main.zig"
No ai used its a one line fix
## What existing issue(s) does this resolve?
N/A

## Pre-requisites

- [x] I have tested & confirmed the changes work locally
- [x] I have read and fully adhere to the rules set in the contributing guidelines found in `CONTRIBUTING.md`

I have tested on Musl alpine and Glibc artix they now render the same with the same config.lua

Reviewed-on: https://codeberg.org/fairyglade/ly/pulls/1070
Reviewed-by: AnErrupTion <anerruption+codeberg@disroot.org>

src/main.zig

@@ -1961,7 +1961,7 @@ fn updateBigClock(self: *BigLabel, ptr: *anyopaque) !void {
             "%M",
             if (state.config.bigclock_seconds) separator else "",
             if (state.config.bigclock_seconds) "%S" else "",
-            if (state.config.bigclock_12hr) "%P" else "",
+            if (state.config.bigclock_12hr) "%p" else "",
         },
         0,
     );