remove special code path for unknown tokens

src/test/ui/parser/lex-bad-token.rs

@@ -1 +1,3 @@
 ● //~ ERROR: unknown start of token
+
+fn main() {}

src/test/ui/parser/lex-stray-backslash.rs

@@ -1 +1,3 @@
 \ //~ ERROR: unknown start of token: \
+
+fn main() {}

src/test/ui/parser/unicode-quote-chars.rs

@@ -4,4 +4,7 @@ fn main() {
     println!(“hello world”);
     //~^ ERROR unknown start of token: \u{201c}
     //~^^ HELP Unicode characters '“' (Left Double Quotation Mark) and '”' (Right Double Quotation Mark) look like '"' (Quotation Mark), but are not
+    //~^^^ ERROR unknown start of token: \u{201d}
+    //~^^^^ HELP Unicode character '”' (Right Double Quotation Mark) looks like '"' (Quotation Mark), but it is not
+    //~^^^^^ ERROR expected token: `,`
 }

src/test/ui/parser/unicode-quote-chars.stderr

@@ -8,5 +8,21 @@ help: Unicode characters '“' (Left Double Quotation Mark) and '”' (Right Dou
 LL |     println!("hello world");
    |              ^^^^^^^^^^^^^
 
-error: aborting due to previous error
+error: unknown start of token: \u{201d}
+  --> $DIR/unicode-quote-chars.rs:4:26
+   |
+LL |     println!(“hello world”);
+   |                          ^
+help: Unicode character '”' (Right Double Quotation Mark) looks like '"' (Quotation Mark), but it is not
+   |
+LL |     println!(“hello world");
+   |                          ^
+
+error: expected token: `,`
+  --> $DIR/unicode-quote-chars.rs:4:21
+   |
+LL |     println!(“hello world”);
+   |                     ^^^^^ expected `,`
+
+error: aborting due to 3 previous errors