Twenty Nineteen: Center-aligned images in columns break beyond the column boundaries.

[kjellr]

As reported over in the Gutenberg repository:
​https://github.com/WordPress/gutenberg/issues/15832

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Center-aligned images within columns in Twenty Nineteen inherit an incorrect max-width, which forces them to extend beyond the column itself:

The attached patch corrects this by limiting the max-width of the image's figure wrapper to 100%:

[SergeyBiryukov]

In 45897:

Twenty Nineteen: Make sure center-aligned images in columns do not break beyond the column boundaries.

Props kjellr.
Fixes #47937.

[sabernhardt]

#47290 was marked as a duplicate.