bump higher

Signed-off-by: xxchan <[email protected]>

Author: xxchan

ci/rust-toolchain

@@ -4,4 +4,4 @@
 # 3. (optional) **follow the instructions in lints/README.md** to update the toolchain and dependencies for lints
 
 [toolchain]
-channel = "nightly-2024-06-08"
+channel = "nightly-2024-06-20"