Wrong requirements support for Mac x86

[Norfolks]

I am working on a pretty oldish MacBook Pro 2015.
And I have runtime issues with starting a sandbox for all new workspaces releases down to version 11.1, however, it is mentioned that this setup is supported.
Log example:

error: failed to run custom build command for `near-workspaces v0.14.1`

Caused by:
  process didn't exit successfully: `/Users/Nick/Projects/mem-starter/target/debug/build/near-workspaces-376981cba5e4ceef/build-script-build` (exit status: 101)
  --- stdout
  cargo:rerun-if-env-changed=NEAR_SANDBOX_BIN_PATH

  --- stderr
  thread 'main' panicked at /Users/Nick/.cargo/registry/src/index.crates.io-6f17d22bba15001f/near-workspaces-0.14.1/build.rs:7:39:
  Could not install sandbox: Unsupported platform: only linux-x86 and darwin-arm are supported
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[frol]

If I remember correctly, there are no near-sandbox pre-built binaries for MacOS x86, so we should update near-sandbox error reporting and the README that it is not supported anymore