rpc: Remove outdated info about the simple/ directory

The simple/ directory was removed in https://v.io/c/20357.

Change-Id: Idc1614fc32477f7e456aa6831f65f9e6301080c1
diff --git a/runtime/internal/rpc/benchmark/README.md b/runtime/internal/rpc/benchmark/README.md
index d939979..76af7b8 100644
--- a/runtime/internal/rpc/benchmark/README.md
+++ b/runtime/internal/rpc/benchmark/README.md
@@ -49,19 +49,6 @@
 
 `RESULTS.txt` has the full benchmark results.
 
-## `simple/main.go`
-
-`simple/main.go` is a simple command-line tool to run the main benchmarks to measure
-RPC setup time, latency, and throughput.
-
-```
-$ jiri go run simple/main.go
-RPC Connection  33.48 ms/rpc
-RPC (echo 1000B)  1.31 ms/rpc (763.05 qps)
-RPC Streaming (echo 1000B)  0.11 ms/rpc
-RPC Streaming Throughput (echo 1MB) 313.91 MB/s
-```
-
 # Client/Server
 ## `{benchmark,benchmarkd}/main.go`