docs: fixing example in CONTRIBUTING.md

[asura-io]

Description

The current example rust tests do not work:

$ cargo run --examples basic_operations

error: unexpected argument '--examples' found

  tip: a similar argument exists: '--example'

Usage: cargo run --example [<NAME>] [args]...

For more information, try '--help'.

This also does not work:

$ cargo run --example basic_operations 
error: target `basic_operations` in package `deltalake` requires the features: `datafusion`
Consider enabling them by passing, e.g., `--features="datafusion"`

This does work:

$ cargo run --example basic_operations --features="datafusion"
   Compiling deltalake-core v0.17.0 (/Users/gautham/src/delta-rs/crates/core)
...
...

Making a quick update to the docs so that the example works out of the box.

[github-actions]

ACTION NEEDED

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