fix: skip caching the response if it is a streamable file instance

[jmcdo29]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
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PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

If the CacheIntereceptor is used and a StreamableFile is returned, the class instance won't be properly cached due to serialization of the stream.

Issue Number: #10575

What is the new behavior?

This is the easier fix to do rather than taking the stream and serializing it to something that can be cached in. If we'd rather actually serialize the stream I can work on that functionality instead

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 14da9cb9-8c0b-45d6-a33d-0e8a13d1602a

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.926%

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Totals
Change from base Build 50eb7c20-fcbc-45f9-a835-3c087cce57ff:	0.0%
Covered Lines:	6463
Relevant Lines:	6955

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💛 - Coveralls

[kamilmysliwiec]

lgtm