Update docs on the unstable_features flag.

Author: joaodelgado

README.md

@@ -102,18 +102,16 @@ Currently we accept the following options:
   running `cargo test` rather than `cargo build`. I.e., compiles (but does not
   run) test code.
 * `unstable_features` (`bool`, defaults to `false`) enables unstable features.
-  Currently, this includes range formatting and `workspace_mode`,
-  `analyze_package` options.
+  Currently no option requires this flag.
 * `sysroot` (`String`, defaults to `""`) if the given string is not empty, use
   the given path as the sysroot for all rustc invocations instead of trying to
   detect the sysroot automatically
 * `target` (`String`, defaults to `""`) if the given string is not empty, use
   the given target triple for all rustc invocations
 * `wait_to_build` (`u64`, defaults to `500`) time in milliseconds between
   receiving a change notification and starting build
-* `workspace_mode` (`bool`, defaults to `true`) Experimental mode, requires
-  `unstable_features` turned on. When turned on, RLS will try to scan current
-  workspace and analyze every package in it.
+* `workspace_mode` (`bool`, defaults to `true`) When turned on, RLS will try
+  to scan current workspace and analyze every package in it.
 * `analyze_package` (`String`, defaults to `""`) When `workspace_mode` is
   enabled, analysis will be only provided for the specified package (runs as
   if `-p <analyze_package>` was passed).