disable thunderbird-rust by default

comm-central/patches/9999999-port1860654-suite-bustage.patch

@@ -66,8 +66,8 @@ diff --git a/suite/moz.configure b/suite/moz.configure
  imply_option("MOZ_PLACES", True)
  imply_option("MOZ_SERVICES_SYNC", False)
  
-+# Thunderbird Rust code is now the default
-+option("--disable-thunderbird-rust", help="Enable Rust support within Thunderbird")
++# Enable Rust overrides
++option("--enable-thunderbird-rust", help="Enable Rust support within Thunderbird")
 +
 +set_config("MOZ_THUNDERBIRD_RUST", True, when="--enable-thunderbird-rust")
 +set_define("MOZ_THUNDERBIRD_RUST", True, when="--enable-thunderbird-rust")