docs: Update incorrect import in request mocking example #6897

Job	Run time
lint	1m 10s
test-ui	1m 0s
test-browser (chrome, chromium)	3m 11s
test (ubuntu-latest, 18)	8m 4s
test-browser (firefox, firefox)	3m 0s
test-browser-windows (chrome, chromium)	5m 32s
test (ubuntu-latest, 20)	9m 2s
typecheck	1m 51s
test-browser (edge, webkit)	3m 8s
test-browser-windows (edge, webkit)	5m 33s
test (macos-latest, 20)	9m 45s
test (windows-latest, 20)	12m 59s
	1h 4m 15s

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