Upload: Exclude PNG images from scaling after uploading. Fixes a case where...

Upload: Exclude PNG images from scaling after uploading. Fixes a case where resizing a very large PNG may create a scaled image that has smaller dimensions but larger file size than the original.

Fixes #48736.
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git-svn-id: https://core.svn.wordpress.org/trunk@46609 1a063a9b-81f0-0310-95a4-ce76da25c4cd