maven-helper: cope with MITM web caches

Ignacio Arganda-Carreras reported that one shy colleague of his
encountered a problem with building Fiji. The reason was identified as
a different HTTP version being reported than the maven helper expected,
due to a transparent web cache reporting version 1.0 while the ImageJ
artifact repository server reports 1.1.

Let's be a little bit more lenient and allow for HTTP/1.<any-digit>.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>