submodules: Update openvr version requirement

Since
ValveSoftware@84b4863
introduced changes to openvr subproject (or maybe before) this package
won't compile if `openvr` package is installed on ArchLinux (currently
on v2.2.3). Update version requirement to use the subproject if
available.

meson.build

@@ -50,7 +50,7 @@ dep_wayland = dependency('wayland-client')
 vulkan_dep = dependency('vulkan')
 
 if get_option('enable_openvr_support')
-  openvr_dep = dependency('openvr', version: '>= 2', required : false)
+  openvr_dep = dependency('openvr', version: '>= 2.7', required : false)
   if not openvr_dep.found()
     cmake = import('cmake')
     openvr_var = cmake.subproject_options()