[IMPROVEMENT] getting rid of the warnings during rust builds

[ArchitBhonsle]

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#1469 brought this up where we would get some warnings when compiling the rust module without the hardsubx_ocr feature. As stated later in the issue these muts are actually necessary when the feature is turned on. This fix is a minor change which removes the warnings in both the cases. This might allow us to maybe use RUSTFLAGS="--deny warnings" in our workflows to fail on warnings.

[ArchitBhonsle]

Hi @cfsmp3 ! Could you check this out? It's just a minor quality of life fix and gets rid of the Rust warnings.

[cfsmp3]

I assigned the review to @PunitLodha , he's been doing the Rust side of things around here :-)

[PunitLodha]

Looks good