Use a locked cargo install in deploy.yml

[jobarr-amzn]

Description of changes:

This should fix the failure in deploy.yml that we have seen most recently:

2025-03-17 19:21:11 [INFO] (mdbook::book): Running the html backend

thread 'main' panicked at /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/elasticlunr-rs-3.0.3/src/lang/en.rs:518:47:
index out of bounds: the len is 3 but the index is 18446744073709551615
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
    Liquid Warning: Liquid syntax error (line 75): [:end_of_string] is not a valid expression in "{{}}" in index.md
                    done in 1.444 seconds.
 Auto-regeneration: disabled. Use --watch to enable.

For more information, see mattico/elasticlunr-rs#57, the mitigation comes from a recommendation from the mdBook maintainers.

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