fix: Use transitioned target platform for `platform_transition_test` #4909

Job	Run time
matrix-prep	6s
test (7, 7.3.2, 1, ubuntu, .)	6m 7s
test (7, 7.3.2, 1, ubuntu, e2e/copy_action)	19s
test (7, 7.3.2, 1, ubuntu, e2e/copy_to_directory)	1m 14s
test (7, 7.3.2, 1, ubuntu, e2e/coreutils)	24s
test (7, 7.3.2, 1, ubuntu, e2e/external_copy_to_directory)	1m 11s
test (7, 7.3.2, 1, ubuntu, e2e/smoke)	1m 12s
test (7, 7.3.2, 1, ubuntu, e2e/write_source_files)	18s
test (7, 7.3.2, 0, ubuntu, e2e/copy_action)	18s
test (7, 7.3.2, 0, ubuntu, e2e/copy_to_directory)	57s
test (7, 7.3.2, 0, ubuntu, e2e/coreutils)	19s
test (7, 7.3.2, 0, ubuntu, e2e/external_copy_to_directory)	1m 2s
test (7, 7.3.2, 0, ubuntu, e2e/smoke)	48s
test (7, 7.3.2, 0, ubuntu, e2e/write_source_files)	17s
test (6, 6.5.0, 0, ubuntu, e2e/copy_action)	23s
test (6, 6.5.0, 0, ubuntu, e2e/copy_to_directory)	54s
test (6, 6.5.0, 0, ubuntu, e2e/coreutils)	23s
test (6, 6.5.0, 0, ubuntu, e2e/external_copy_to_directory)	53s
test (6, 6.5.0, 0, ubuntu, e2e/smoke)	1m 3s
test (6, 6.5.0, 0, ubuntu, e2e/write_source_files)	16s
conclusion	4s
	18m 28s

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