Documentation: remove SH-5 index entries

Remove SH-5 documentation index entries following the removal
of SH-5 source code.

Error: Cannot open file ../arch/sh/mm/tlb-sh5.c
Error: Cannot open file ../arch/sh/mm/tlb-sh5.c
Error: Cannot open file ../arch/sh/include/asm/tlb_64.h
Error: Cannot open file ../arch/sh/include/asm/tlb_64.h

Fixes: 3b69e8b4

 ("Merge tag 'sh-for-5.8' of git://git.libc.org/linux-sh")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Rich Felker <dalias@libc.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: ysato@users.sourceforge.jp
Cc: linux-sh@vger.kernel.org
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>