Update examples to work latest nightly rustc

[mukilan]

Context: Recent PRs are failing in CI because examples don't compile.

error: could not compile `webrender` (lib) due to previous error
   Compiling webrender v0.60.0
error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
  --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/webrender-0.60.0/src/record.rs:34:13
   |
34 |             mem::transmute::<TypeId, u64>(TypeId::of::<ApiMsg>())
   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: source type: `TypeId` (128 bits)
   = note: target type: `u64` (64 bits)

The example code uses webrender v0.60.0 which is quite old and the offending code causing above error has been removed from webrender https://github.com/servo/webrender/commit/e8d2d7d6

We should publish a new webrender version to crates.io and update the examples as necessary.