fix: add automatically generated testindex to gitignore #5860

Job	Run time
check_format_and_unit_tests	1m 8s
build / Special integration tests (21)	1m 8s
build / Special integration tests (25)	1m 9s
build / Special integration tests (17)	1m 9s
build / integration_tests (21, 1.30.12) / Integration tests (21, 1.30.12, vertx)	1m 2s
build / integration_tests (21, 1.33.1) / Integration tests (21, 1.33.1, vertx)	1m 2s
build / integration_tests (17, 1.31.8) / Integration tests (17, 1.31.8, vertx)	1m 2s
build / integration_tests (21, 1.31.8) / Integration tests (21, 1.31.8, vertx)	1m 2s
build / integration_tests (21, 1.32.4) / Integration tests (21, 1.32.4, vertx)	1m 3s
build / integration_tests (25, 1.30.12) / Integration tests (25, 1.30.12, vertx)	1m 3s
build / integration_tests (25, 1.31.8) / Integration tests (25, 1.31.8, vertx)	59s
build / integration_tests (25, 1.33.1) / Integration tests (25, 1.33.1, vertx)	1m 0s
build / integration_tests (25, 1.32.4) / Integration tests (25, 1.32.4, vertx)	1m 0s
build / integration_tests (17, 1.30.12) / Integration tests (17, 1.30.12, vertx)	1m 1s
build / integration_tests (17, 1.32.4) / Integration tests (17, 1.32.4, vertx)	57s
build / integration_tests (17, 1.33.1) / Integration tests (17, 1.33.1, vertx)	1m 0s
build / httpclient-tests (vertx) / Integration tests (25, 1.32.0, vertx)	1m 1s
build / httpclient-tests (jdk) / Integration tests (25, 1.32.0, jdk)	1m 2s
build / httpclient-tests (jetty) / Integration tests (25, 1.32.0, jetty)	59s
	19m 47s

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