Emphasize borrowing rule in C docs (#1422)

* Emphasize borrowing rule in C docs

Missing this "not" wasted an hour of my time 😅

* Use a pinned nightly

---------

Co-authored-by: Alex Crichton <alex@alexcrichton.com>

Author: MendyBerger

.github/workflows/main.yml

@@ -147,10 +147,11 @@ jobs:
     - run: cargo test -p wit-bindgen --all-features
     - run: cargo test -p wit-bindgen-rust
     - run: cargo test --workspace --exclude 'wit-bindgen*'
-    - run: rustup update nightly --no-self-update
-    - run: rustup component add miri --toolchain nightly
-    - run: rustup component add rust-src --toolchain nightly
-    - run: cargo +nightly miri test -p wit-bindgen --all-features
+    - run: rustup update nightly-2025-11-10 --no-self-update
+    - run: rustup default nightly-2025-11-10
+    - run: rustup component add miri
+    - run: rustup component add rust-src
+    - run: cargo miri test -p wit-bindgen --all-features
 
   check:
     name: Check

crates/c/README.md

@@ -479,7 +479,7 @@ The importing component's responsibility for dropping borrows of imported resour
 - If the borrow was passed as an argument to one of the importing component's exports:
     - If the bindings were generated with `--autodrop-borrows=yes`, then borrowed handles will be automatically dropped when the exported function returns; no additional action is required by importing component
     - If the bindings were generated with `--autodrop-borrow=no`, or this command line option was not supplied, then the importing component must drop the borrowed handle by calling the generated `*_drop_borrow` function.
-- If the component obtained the borrow by calling `*_borrow*_` on an owned resource, it must not call `*_drop_borrow`
+- If the component obtained the borrow by calling `*_borrow*_` on an owned resource, it must **not** call `*_drop_borrow`
 
 Here is a potential implementation of the `run` export that correctly handles the lifetime of the owned cat resource retrieved from `get-cat-by-name`: