runtime: Drop 'sh' highlighting from fenced code blocks

Because these are shell sessions, not scripts (e.g. we don't want
'for' in the version output highlighted as a keyword).  Rolls back
4dfe30b ('sh' syntax highlighting for fenced code blocks,
2015-09-14).

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

runtime.md

@@ -36,7 +36,8 @@ Print the runtime version and exit.
 * *Exit code:* The runtime MUST exit with zero.
 
 Example:
-```sh
+
+```
 $ funC version
 funC 1.0.0
 Built for x86_64-pc-linux-gnu
@@ -59,7 +60,8 @@ Start a container from a bundle directory.
 * *Exit code:* The runtime MUST exit with the application process's exit code.
 
 Example:
-```sh
+
+```
 # in a bundle directory with a process that echos "hello" and exits 42
 $ funC start --id hello-1
 hello