Remove use of illegal ":version" HTTP pseudo-header in tests
According to the specs, implementations of HTTP/2 and HTTP/3 MUST NOT send any header whose name starts with a colon (":") except for ":method", ":scheme", ":authority", and ":path".
(Not to mention the fact that HTTP/1.1 is not the correct version of HTTP being used here...)
https://tools.ietf.org/html/draft-ietf-quic-http-24#section-4.1.1
https://tools.ietf.org/html/rfc7540#section-8.1.2.1
gfe-relnote: n/a, test-only change
PiperOrigin-RevId: 281059854
Change-Id: Ic8e7422c8f65c2f702eb899b73dcbd302e9ab945