Update the error thrown by Bazel

Hello,

The error message thrown by Bazel in step 4 should be updated.
The label of the toolchain specified in step 3 is **//toolchain:asmjs_toolchain** and not **//toolchain:asmjs_toolchain_config**.
Therefore the error message should be
```
    Rule '//toolchain:asmjs_toolchain' does not exist
```

Closes #10509.

PiperOrigin-RevId: 294818454
diff --git a/site/docs/tutorial/cc-toolchain-config.md b/site/docs/tutorial/cc-toolchain-config.md
index fec1470..d1ab3af 100644
--- a/site/docs/tutorial/cc-toolchain-config.md
+++ b/site/docs/tutorial/cc-toolchain-config.md
@@ -139,7 +139,7 @@
 4.  Run the build again. Bazel throws the following error:
 
     ```
-    Rule '//toolchain:asmjs_toolchain_config' does not exist
+    Rule '//toolchain:asmjs_toolchain' does not exist
     ```
 
     Now you need to define `cc_toolchain` targets for every value in the