chore: only add BackendTLSPolicy when Gateway API is installed in the cluster #523

Job	Run time
ensure-actions-sha-pin	2s
lint	16s
golden-tests	34s
integration-test (1.27.16, kong)	1m 55s
lint-test (1.31.4, kong)	11m 38s
integration-test (1.27.16, ingress)	2m 0s
oldversion-integration-test (2.10, 3.3, kong)	1m 37s
lint-test (1.31.4, ingress)	3m 49s
oldversion-integration-test (2.10, 3.3, ingress)	1m 30s
integration-test (1.27.16, gateway-operator)	1m 39s
lint-test (1.31.4, gateway-operator)	4m 33s
integration-test (1.28.15, kong)	1m 41s
oldversion-integration-test (2.10, 3.2, kong)	1m 29s
oldversion-integration-test (2.10, 3.2, ingress)	1m 42s
integration-test (1.28.15, ingress)	1m 49s
integration-test (1.28.15, gateway-operator)	1m 37s
integration-test (1.29.12, kong)	1m 48s
oldversion-integration-test (2.11, 3.3, kong)	1m 33s
integration-test (1.29.12, ingress)	1m 47s
oldversion-integration-test (2.11, 3.3, ingress)	1m 27s
oldversion-integration-test (2.11, 3.2, kong)	1m 41s
integration-test (1.29.12, gateway-operator)	1m 39s
integration-test (1.30.8, kong)	1m 55s
oldversion-integration-test (2.11, 3.2, ingress)	1m 38s
integration-test (1.30.8, ingress)	1m 46s
integration-test (1.30.8, gateway-operator)	1m 43s
integration-test (1.31.4, kong)	1m 53s
integration-test (1.31.4, ingress)	1m 46s
integration-test (1.31.4, gateway-operator)	1m 31s
integration-test (1.32.0, kong)	1m 36s
integration-test (1.32.0, ingress)	1m 41s
integration-test (1.32.0, gateway-operator)	1m 25s
passed	1s
	1h 4m 41s

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