macOS 15 arm64: do not install openJDK from Homebrew

Homebrew's OpenJDK install triggers a fontconfig post-install that fails
because the FreeType 2.15.0 bottle references a missing system library.
Freetype is installed by brew in 26-freetype.sh which recently updated
from 2.14.3 to 2.15.0 in brew.

macOS 15 arm64 is the only macOS that installs openJDK. Leave it out,
anything using JDK should use the already installed Zulu JDK instead.

Pick-to: 6.12
Change-Id: I7ebcb3ee26912fa0b1a06b7bda5b94af567ff407
Reviewed-by: Simo Fält <simo.falt@qt.io>