Close FileOutputStream delegate in InspectingOutputStream

InspectingOutputStream extends OutputStream but does not override
close(). When content exceeds MEMORY_LIMIT (approximately 4 KB),
convertToTempFile() replaces the ByteArrayOutputStream delegate with a
FileOutputStream. The try-with-resources in InspectedContent.of() calls
close(), which inherits the no-op OutputStream.close(), leaving the
FileOutputStream open and leaking a file descriptor.

Override close() to delegate to the underlying stream.

See gh-50639

Signed-off-by: Sebastien Tardif <sebtardif@ncf.ca>