Workaround for rust-lang/cargo#10788

As described in Cargo Issue 10788, until Rust 1.71 there were
cases where the dependency/feature syntax would not work correctly
when used in combination with the dep:dependency syntax. Workarounds
include adding an explicit feature

dependency = ["dep:dependency"]

but in many (most?) cases it is enough to only enable the dependency feature
if the dependency is already enabled, via the dependency?/feature
syntax.

For context, here are some workarounds employed by others:
- mstange/samply@89456d4
- alexrudy/tonic@f386954
- jwodder/confab@6f0e2fc

opener/Cargo.toml

@@ -16,7 +16,7 @@ maintenance = { status = "passively-maintained" }
 [features]
 default = ["dbus-vendored"]
 reveal = ["dep:url", "dep:dbus", "windows-sys/Win32_System_Com"]
-dbus-vendored = ["dbus/vendored"]
+dbus-vendored = ["dbus?/vendored"]
 
 [target.'cfg(target_os = "linux")'.dependencies]
 bstr = "1"