[clangd][NFC] Update background-index command line description

Summary:
We didn't change this in D64019 just in case we revert it back.
Deleting it now.

Reviewers: hokein, sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D66943

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@370367 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/clangd/tool/ClangdMain.cpp b/clangd/tool/ClangdMain.cpp
index a3d9401..4cb6604 100644
--- a/clangd/tool/ClangdMain.cpp
+++ b/clangd/tool/ClangdMain.cpp
@@ -122,8 +122,7 @@
 opt<bool> EnableBackgroundIndex{
     "background-index",
     cat(Features),
-    desc("Index project code in the background and persist index on disk. "
-         "Experimental"),
+    desc("Index project code in the background and persist index on disk."),
     init(true),
 };