binutils-native: drop the gcc13 dependency

gcc13 was still being built despite gcc-native/rust-native being
deferred, and it failed the whole build: binutils-native pulled it
transitively. It is the same dependency pattern already removed from
gcc-native -- what the recipe actually needs is a cross compiler, and
that comes from the prefix toolchain on PATH
(x86_64-unknown-redox-gcc, now 16.1.0), not from a cooked gcc13 package.

Keeping it meant building GCC 13 with GCC 16, which does not work: the
host link fails with the libstdc++ 128-bit float helpers unresolved
(__eqtf2/__getf2/__gttf2/__letf2/__unordtf2 against
/usr/lib/gcc/x86_64-pc-linux-gnu/16/libstdc++.so), a host/target libgcc
leak, and beyond that GCC 16 ICEs on GCC 13's libsupc++. See
local/docs/NATIVE-TOOLCHAIN-WORKSTREAM.md.

binutils-native cooks clean without it.

local/recipes/dev/binutils-native/recipe.toml

@@ -8,7 +8,12 @@ same_as = "../../../../recipes/dev/binutils-gdb"
 [build]
 template = "custom"
 dependencies = [
-    "gcc13",
+    # gcc13 dropped: it drags the GCC 13 cross compiler into the graph, which
+    # no longer builds (GCC 16 ICEs compiling GCC 13's libsupc++ -- see
+    # local/docs/NATIVE-TOOLCHAIN-WORKSTREAM.md) and which nothing here needs.
+    # The cross compiler comes from the prefix toolchain on PATH,
+    # x86_64-unknown-redox-gcc, now 16.1.0. Same change already made to
+    # gcc-native.
     "gnu-binutils",
     "libgmp",
     "libmpfr",