Revert the lexing of c_str_literals

compiler/rustc_lexer/src/lib.rs

@@ -367,13 +367,6 @@ impl Cursor<'_> {
                 Some(|terminated| Byte { terminated }),
             ),
 
-            // c-string literal, raw c-string literal or identifier.
-            'c' => self.c_or_byte_string(
-                |terminated| CStr { terminated },
-                |n_hashes| RawCStr { n_hashes },
-                None,
-            ),
-
             // Identifier (this should be checked after other variant that can
             // start as identifier).
             c if is_id_start(c) => self.ident_or_unknown_prefix(),