Bump postcss-import from 15.1.0 to 16.0.1 #1576

Job	Run time
Pre run	4s
Lint: JS	1m 19s
E2E test: JS (1, 2)	11m 52s
Feature tests: PHP ${{ matrix.php }}, WP ${{ matrix.wp }}	0s
Lint: CSS	1m 12s
Lint: PHP	0s
E2E test: JS (2, 2)	11m 22s
Unit test: JS	1m 23s
Static Analysis: PHP	0s
Unit test: PHP 8.0, WP latest	21s
Build: ${{ matrix.build }} build ZIP	0s
Unit test: PHP 8.3, WP trunk	24s
Unit test: PHP 8.2, WP trunk	23s
Unit test: PHP 8.1, WP trunk	23s
Unit test: PHP 8.0, WP trunk	23s
Unit test (with coverage): PHP 8.0, WP latest	22s
Unit test: PHP 8.0, WP latest	21s
Unit test: PHP 7.4, WP latest	24s
Unit test: PHP 7.4, WP latest	22s
Unit test: PHP 7.4, WP 5.3	22s
Unit test: PHP 7.4, WP 5.3	24s
Upload plugin ZIPs to Google Cloud Storage	0s
Comment on PR with links to plugin ZIPs	0s
	31m 21s

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