Put back punctuation in comments

Author: oisyn

rust-toolchain

@@ -1,13 +1,13 @@
-# If you see this, run `rustup self update` to get rustup 1.23 or newer
+# If you see this, run `rustup self update` to get rustup 1.23 or newer.
 
-# NOTE: above comment is for older `rustup` (before TOML support was added)
+# NOTE: above comment is for older `rustup` (before TOML support was added),
 # which will treat the first line as the toolchain name, and therefore show it
-# to the user in the error, instead of "error: invalid channel name '[toolchain]'"
+# to the user in the error, instead of "error: invalid channel name '[toolchain]'".
 
 [toolchain]
 channel = "nightly-2023-01-21"
 components = ["rust-src", "rustc-dev", "llvm-tools-preview"]
 # commit_hash = 5ce39f42bd2c8bca9c570f0560ebe1fce4eddb14
 
 # Whenever changing the nightly channel, update the commit hash above, and make
-# sure to change REQUIRED_TOOLCHAIN in crates/rustc_codegen_spirv/src/build.rs also
+# sure to change REQUIRED_TOOLCHAIN in crates/rustc_codegen_spirv/src/build.rs also.