examples/rust: Switch to using resolver 2

When building the Rust examples we see a warning:

  > warning: some crates are on edition 2021 which defaults to
  >          `resolver = "2"`, but virtual workspaces default to `resolver = "1"`
  > note: to keep the current resolver, specify `workspace.resolver = "1"`
  >       in the workspace root's manifest
  > note: to use the edition 2021 resolver, specify `workspace.resolver = "2"`
  >       in the workspace root's manifest

Fix it by switching to resolver 2.

Signed-off-by: Daniel Müller <deso@posteo.net>

Author: d-e-s-o

examples/rust/Cargo.toml

@@ -1,4 +1,5 @@
 [workspace]
+resolver = "2"
 members = [
   "tracecon",
   "xdp",