Remove the grammar, point to the reference

[steveklabnik]

This page isn't used anymore, so we should point to the stuff that is.

r? @rust-lang/docs , @Havvy , @alercah

[QuietMisdreavus]

It may be worth updating the reference's introduction to remove its link to this grammar page:

You may also be interested in the grammar.

[rust-highfive]

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:59:21] ........................................................test [run-pass] run-pass/mir_heavy_promoted.rs has been running for over 60 seconds
[00:59:32] ............................................
[00:59:46] ...................................................................................................i
[01:00:32] i...............................................................i...................................
[01:00:51] ................i.ii...............................................test [run-pass] run-pass/saturating-float-casts.rs has been running for over 60 seconds
[01:01:32] ........................iiiiiii.....................................................................
[01:01:49] ....................................................................................................
[01:02:04] ....................................................................................................
[01:02:21] .................................................................................................
---
[01:33:37] travis_fold:end:stage0-linkchecker

[01:33:37] travis_time:end:stage0-linkchecker:start=1526574718333820815,finish=1526574721503254092,duration=3169433277

[01:33:53] reference/tokens.html:586: broken link fragment `#symbols` pointing to `grammar.html`
[01:33:53] reference/types.html:326: broken link fragment `#type-definitions` pointing to `grammar.html`
[01:33:53] reference/notation.html:150: broken link fragment `#special-unicode-productions` pointing to `grammar.html`
[01:33:53] reference/print.html:182: broken link fragment `#special-unicode-productions` pointing to `grammar.html`
[01:33:53] reference/print.html:906: broken link fragment `#symbols` pointing to `grammar.html`
[01:33:53] reference/print.html:5408: broken link fragment `#type-definitions` pointing to `grammar.html`
[01:33:55] thread 'main' panicked at 'found some broken links', tools/linkchecker/main.rs:49:9
[01:33:55] 
[01:33:55] 
[01:33:55] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/linkchecker" "/checkout/obj/build/x86_64-unknown-linux-gnu/doc"
[01:33:55] expected success, got: exit code: 101
[01:33:55] expected success, got: exit code: 101
[01:33:55] 
[01:33:55] 
[01:33:55] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:33:55] Build completed unsuccessfully in 0:44:16
[01:33:55] make: *** [check] Error 1
[01:33:55] Makefile:58: recipe for target 'check' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:004a6358
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[steveklabnik]

Ah, interesting. Let's table this for now and talk about it at the next meeting.