README: fix typo in examples rule

Change-Id: I95d76d9f8a0d4c639ad539c91f8fa4b64ab89dbd
Reviewed-on: https://weave-review.googlesource.com/2200
Reviewed-by: Jacob Marble <jacobmarble@google.com>

README.md

diff --git a/README.md b/README.md
index 5f69b01..fc042b7 100644
--- a/README.md
+++ b/README.md
@@ -99,7 +99,7 @@
 ### Build examples
 
 ```
-make examples-all
+make all-examples
 ```
 
 See [the examples README](/examples/daemon/README.md) for details.