Only discard command comment if prev token was comment (#3628)

This fixes issues where a file with multiple def commands with their own
doc comments, some of the comments would be discarded.

crates/nu-parser/tests/main.rs

@@ -23,3 +23,44 @@ fn defs_contain_comment_in_help() {
         assert!(actual.out.contains("I comment and test. I am a good boy."));
     });
 }
+
+#[test]
+fn defs_contain_multiple_comments_in_help() {
+    Playground::setup("comment_test_2", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContent(
+            "my_def.nu",
+            r#"
+                # I comment and test. I am a good boy.
+                def comment_philosphy [] {
+                    echo It’s not a bug – it’s an undocumented feature. (Anonymous)
+                }
+
+                # I comment and test all my functions. I am a very good boy.
+                def comment_philosphy_2 [] {
+                    echo It’s not a bug – it’s an undocumented feature. (Anonymous)
+                }
+
+
+                # I comment and test all my functions. I am the best boy.
+                def comment_philosphy_3 [] {
+                    echo It’s not a bug – it’s an undocumented feature. (Anonymous)
+                }
+                "#,
+        )]);
+
+        let actual = nu!(cwd: dirs.test(), r#"
+            source my_def.nu
+            help comment_philosphy
+            help comment_philosphy_2
+            help comment_philosphy_3
+            "#);
+
+        assert!(actual.out.contains("I comment and test. I am a good boy."));
+        assert!(actual
+            .out
+            .contains("I comment and test all my functions. I am a very good boy."));
+        assert!(actual
+            .out
+            .contains("I comment and test all my functions. I am the best boy."));
+    });
+}