bench: remove broken benchmarking with a JS shell

Author: fitzgen

bench/README.md

@@ -6,8 +6,6 @@ library.
 Ensure that you have built the library, as these benchmarks rely on
 `dist/source-map.js`. See the main README.md for detais on building.
 
-## Running Within a Browser
-
 Run a local webserver from the root of the repository:
 
 ```
@@ -20,8 +18,3 @@ Open
 in your browser.
 
 Open `bench.html` in a browser and click on the appropriate button.
-
-## Running with a JS Shell
-
-Run `$JS_SHELL bench-shell-bindings.js`, where `$JS_SHELL` is one of `node` or
-SpiderMonkey's `js`.