The "Enable GVT-d in ACRN" tutorial includes a number of rightwards
arrows. The source text used the "→" symbol for this but this
is not valid in ReST files. We add a substitution for this and use it
in the tutorial instead.
Tracked-On: #5769
Signed-off-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>