std.Target: Bump minimum OpenBSD version to 7.5.

Per: https://www.openbsd.org/faq/faq5.html#Flavors

Author: alexrp

lib/std/Target.zig

@@ -518,7 +518,7 @@ pub const Os = struct {
                 },
                 .openbsd => .{
                     .semver = .{
-                        .min = .{ .major = 7, .minor = 3, .patch = 0 },
+                        .min = .{ .major = 7, .minor = 5, .patch = 0 },
                         .max = .{ .major = 7, .minor = 6, .patch = 0 },
                     },
                 },