cli/command/image: close ProgressReader

[thaJeztah]

progress.NewProgressReader implements io.ReadCloser. client.ImageBuild only requests an io.Reader, and there's some code in place to assert if the passed io.Reader was an io.ReadCloser, but let's make sure it's closed just in case.

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[codecov-commenter]

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[thaJeztah]

Ah, hm.. yeah, looks like this won't work, or needs looking into;

--- FAIL: TestRunBuildDockerfileFromStdinWithCompress (0.00s)
    build_test.go:53: assertion failed: error is not nil: io: read/write on closed pipe
--- FAIL: TestRunBuildDockerfileOutsideContext (0.00s)
    build_test.go:113: assertion failed: error is not nil: io: read/write on closed pipe
time="2026-02-19T10:12:59Z" level=error msg="Can't add file /private/var/folders/75/ggvb9t6x5mlbs46lkdhlcbyc0000gn/T/TestRunBuildDockerfileOutsideContext-1024026542/data to tar: io: read/write on closed pipe"
time="2026-02-19T10:12:59Z" level=error msg="Can't close tar writer: io: read/write on closed pipe"
time="2026-02-19T10:13:00Z" level=error msg="Can't close tar writer: io: read/write on closed pipe"
time="2026-02-19T10:13:00Z" level=error msg="Can't add file /private/var/folders/75/ggvb9t6x5mlbs46lkdhlcbyc0000gn/T/TestRunBuildWithSymlinkedContext-2937020932/context/Dockerfile to tar: io: read/write on closed pipe"
time="2026-02-19T10:13:00Z" level=error msg="Can't close tar writer: io: read/write on closed pipe"
--- FAIL: TestRunBuildWithSymlinkedContext (0.00s)
    build_test.go:172: assertion failed: error is not nil: io: read/write on closed pipe