chore: standardize notes: to note: in file entries

240 file-level entries used notes: instead of the canonical note:
field. verify.py and cross_reference.py only read note:, so these
were silently ignored.

emulators/vice_x64dtv.yml

@@ -25,7 +25,7 @@ files:
     hle_fallback: true
     size: 2097152
     source_ref: "vice/src/c64dtv/c64dtvflash.c:59-64,470-471,488-505"
-    notes: >
+    note: >
       Loaded via sysfile_load from system/vice/C64DTV/. All model variants
       (V2 PAL/NTSC, V3 PAL/NTSC, Hummer) default to this filename. If not
       found, the core copies embedded BASIC, kernal and chargen ROMs into