build: Switch from YAML format for sources list to JSON format

Signed-off-by: Felicitas Pojtinger <felicitas@pojtinger.com>

Author: pojntfx

com.pojtinger.felicitas.Multiplex.json

@@ -39,7 +39,7 @@
         "install -D -m 0644 internal/resources/$FLATPAK_ID.metainfo.xml /app/share/metainfo/$FLATPAK_ID.metainfo.xml",
         "for icon in 16x16 22x22 24x24 32x32 36x36 48x48 64x64 72x72 96x96 128x128 192x192 256x256 512x512; do install -D -m 0644 docs/icon-${icon}.png /app/share/icons/hicolor/${icon}/apps/$FLATPAK_ID.png; done"
       ],
-      "sources": [{ "type": "dir", "path": "." }, "go.mod.yml"]
+      "sources": [{ "type": "dir", "path": "." }, "go.mod.json"]
     }
   ]
 }