std.Target: bump min-max versions for OpenBSD from 7.6-7.7 to 7.7-7.8

https://cdn.openbsd.org/pub/OpenBSD/7.8/ANNOUNCEMENT

Author: alexrp

lib/std/Target.zig

@@ -554,8 +554,8 @@ pub const Os = struct {
                 },
                 .openbsd => .{
                     .semver = .{
-                        .min = .{ .major = 7, .minor = 6, .patch = 0 },
-                        .max = .{ .major = 7, .minor = 7, .patch = 0 },
+                        .min = .{ .major = 7, .minor = 7, .patch = 0 },
+                        .max = .{ .major = 7, .minor = 8, .patch = 0 },
                     },
                 },