examples: README: remove sh tags

The markdown renderer for grpc.io doesn't know what to do with the tags
with the syntax highlighting tag like:

```
```sh
```

See http://www.grpc.io/docs/installation/go.html

examples/README.md

@@ -10,7 +10,8 @@ PREREQUISITES
 
 - This requires Go 1.4
 - Requires that [GOPATH is set](https://golang.org/doc/code.html#GOPATH)
-```sh
+
+```
 $ go help gopath
 $ # ensure the PATH contains $GOPATH/bin
 $ export PATH=$PATH:$GOPATH/bin
@@ -19,7 +20,7 @@ $ export PATH=$PATH:$GOPATH/bin
 INSTALL
 -------
 
-```sh
+```
 $ go get -u github.com/grpc/grpc-go/examples/helloworld/greeter_client
 $ go get -u github.com/grpc/grpc-go/examples/helloworld/greeter_server
 ```
@@ -28,12 +29,14 @@ TRY IT!
 -------
 
 - Run the server
-```sh
+
+```
 $ greeter_server &
 ```
 
 - Run the client
-```sh
+
+```
 $ greeter_client
 ```
 
@@ -45,7 +48,8 @@ OPTIONAL - Rebuilding the generated code
   - This is will change once proto3 is officially released
 
 2 Install the protoc Go plugin.
-```sh
+
+```
 $ go get -a github.com/golang/protobuf/protoc-gen-go
 $
 $ # from this dir; invoke protoc