Fix default docker_observer endpoint on Windows #85606

Job	Run time
windows-unittest-matrix (receiver-0)	2m 41s
windows-unittest-matrix (receiver-1)	2m 43s
windows-unittest-matrix (receiver-2)	2m 34s
windows-unittest-matrix (receiver-3)	2m 43s
windows-unittest-matrix (processor-0)	2m 39s
windows-unittest-matrix (processor-1)	2m 41s
windows-unittest-matrix (exporter-0)	2m 44s
windows-unittest-matrix (exporter-1)	2m 43s
windows-unittest-matrix (exporter-2)	2m 43s
windows-unittest-matrix (exporter-3)	2m 39s
windows-unittest-matrix (extension)	2m 44s
windows-unittest-matrix (connector)	2m 44s
windows-unittest-matrix (internal)	2m 41s
windows-unittest-matrix (pkg)	2m 42s
windows-unittest-matrix (cmd-0)	2m 43s
windows-unittest-matrix (cmd-1)	2m 46s
windows-unittest-matrix (other)	2m 35s
windows-unittest	1s
	45m 46s

Provide feedback