Deprecate --experimental_ui / --ui

PiperOrigin-RevId: 248280268

src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
index c5b651d..9a4bae2 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeCommandEventHandler.java
@@ -201,6 +201,7 @@
                 + "workspace directory or one of the directories specified by --package_path.")
     public boolean attemptToPrintRelativePaths;
 
+    @Deprecated
     @Option(
         name = "ui",
         oldName = "experimental_ui",