[FREELDR:PC98] Fix build by doing a partial revert

Partial revert of 9decadee832de852a690c4005b0be488995fb7ab.
It introduced a typo in the assembler code that broke the build.
Also, "Press any key" text fits into 512 bootsector space on both GCC/MSVC.

CORE-19882 CORE-17977

boot/freeldr/bootsect/pc98/fat12fdd.S

···
 msgNotFoundError:
     .ascii "NFE", CR, LF, NUL
 msgAnyKey:
-//  .ascii "Press any key", NUL
-    .ascii "Press key", NULL
+    .ascii "Press any key", NUL
 filename:
     .ascii "FREELDR SYS"