x86/virt/tdx: Remove kexec docs

x86/virt/tdx: Remove kexec docs

Recent changes have removed the hard limitations for using kexec and
TDX together. So remove the section in the TDX docs.

Users on partial write erratums will need an updated TDX module to
handle the rare edge cases. The docs do not currently provide any
guidance on recommended TDX module versions, so don't keep a whole
section around to document this interaction.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20260402-fuller_tdx_kexec_support-v3-5-34438d7094bf@intel.com