Revert #286: Add C-string literals.

This reverts commit 5a4e7ba, reversing
changes made to 34fca48.

This is being reverted in rust-lang/rust#119528

Author: ehuss

src/SUMMARY.md

@@ -33,4 +33,3 @@
   - [Reserving syntax](rust-2021/reserving-syntax.md)
   - [Warnings promoted to errors](rust-2021/warnings-promoted-to-error.md)
   - [Or patterns in macro-rules](rust-2021/or-patterns-macro-rules.md)
-  - [C-string literals](rust-2021/c-string-literals.md)