pgo: full-inner: add --override tweak.grapheme-shaping=no

Grapheme shaping is now enabled by default in foot. However, when
generating the profiling data in PGO builds, this results in skewed
optimizations.

The end result is worse benchmark results regardless of whether
grapheme-shaping is enabled or not (when running the benchmarks).

pgo/full-inner.sh

@@ -18,6 +18,7 @@ cd "${blddir}"
 "${blddir}"/footclient --version
 "${blddir}"/foot \
            --config=/dev/null \
+           --override tweak.grapheme-shaping=no \
            --term=xterm \
         sh -c "
           set -eux