Rollup merge of #138735 - jieyouxu:drop-llvm-alias, r=nikic

Remove `llvm` and `llvms` triagebot ping aliases for `icebreakers-llvm` ping group

Because it's way too easy to confuse LLVM Icebreakers ping group versus trying to ping WG-llvm.
And AFAIK, icebreakers-llvm isn't really used in a good while.

I also fixed the rustc-dev-guide docs about ``@rustbot` ping llvm` (and changed that to the raw ping group name ``@rustbot` icebreakers-llvm`) because it's very confusing.

Previously discussed in [#t-compiler/wg-llvm > Ping group renaming](https://rust-lang.zulipchat.com/#narrow/channel/187780-t-compiler.2Fwg-llvm/topic/Ping.20group.20renaming/with/453005029).

FYI `@rust-lang/wg-llvm`
FYI `@RalfJung` (since you asked in rust-lang/rust#138120 (comment))
r? `@nikic` (or wg-llvm)

Author: matthiaskrgr

src/notification-groups/about.md

@@ -23,7 +23,7 @@ Here's the list of the notification groups:
 - [ARM](./arm.md)
 - [Cleanup Crew](./cleanup-crew.md)
 - [Emscripten](./emscripten.md)
-- [LLVM](./llvm.md)
+- [LLVM Icebreakers](./llvm.md)
 - [RISC-V](./risc-v.md)
 - [WASI](./wasi.md)
 - [WebAssembly](./wasm.md)
@@ -83,7 +83,7 @@ group. For example:
 @rustbot ping arm
 @rustbot ping cleanup-crew
 @rustbot ping emscripten
-@rustbot ping llvm
+@rustbot ping icebreakers-llvm
 @rustbot ping risc-v
 @rustbot ping wasi
 @rustbot ping wasm

src/notification-groups/llvm.md

@@ -1,13 +1,16 @@
-# LLVM Notification group
+# LLVM Icebreakers Notification group
 
 **Github Label:** [A-LLVM] <br>
-**Ping command:** `@rustbot ping llvm`
+**Ping command:** `@rustbot ping icebreakers-llvm`
 
 [A-LLVM]: https://github.com/rust-lang/rust/labels/A-LLVM
 
-The "LLVM Notification Group" are focused on bugs that center around LLVM.
-These bugs often arise because of LLVM optimizations gone awry, or as
-the result of an LLVM upgrade. The goal here is:
+*Note*: this notification group is *not* the same as the LLVM working group
+(WG-llvm).
+
+The "LLVM Icebreakers Notification Group" are focused on bugs that center around
+LLVM. These bugs often arise because of LLVM optimizations gone awry, or as the
+result of an LLVM upgrade. The goal here is:
 
 - to determine whether the bug is a result of us generating invalid LLVM IR,
   or LLVM misoptimizing;