rtspclientsink: Deactivate pad before removing it from the element

Otherwise we might have a pad floating around that is still activated,
or even finalize a pad that is still activated.
21 jobs for deactivate-before-remove in 73 minutes and 31 seconds (queued for 2 minutes)
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build cerbero fedora x86_64 Build
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build clang fedora x86_64 Build
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build nodebug fedora x86_64 Build
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build fedora x86_64 Build
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build static fedora x86_64 Build
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build cerbero macos x86_64 Build
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build static nodebug fedora x86_64 Build
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build cerbero cross-android universal Build
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