Fix exercise instructions: remove references to underlined words (not supported by platform)

Co-authored-by: Cursor <cursoragent@cursor.com>

04.module

@@ -1,4 +1,4 @@
-$MODULE
+$MODULE
 DIOCO_DOC_ID: lc_anna_roberto_ch04
 TITLE: Capítulo 4: Primeros Malentendidos
 DESCRIPTION: Roberto and Anna face their first domestic conflict and learn to resolve it.
@@ -343,7 +343,7 @@ PROMPT: Anna estudia en la biblioteca. (ayer por la tarde)
 RESPONSE: Ayer por la tarde Anna estudió en la biblioteca.
 
 $EXERCISE Lexical Drill A-2: Direct Object Pronoun Substitution
-INTRO: Replace the underlined object with the correct pronoun (lo, la, los, las).
+INTRO: Replace the direct object noun in the sentence with the correct pronoun (lo, la, los, las).
 INSTRUCTION: Replace the noun with the correct pronoun.
 
 EXAMPLE
@@ -546,7 +546,7 @@ INTRO: Direct object pronouns replace the noun that receives the direct action o
 - "Olvidémos{lo}."
 
 $EXERCISE Learning Drill: Direct Object Pronouns
-INTRO: Replace the underlined word with lo, la, los, las.
+INTRO: Replace the direct object noun with the correct pronoun: lo, la, los, las.
 INSTRUCTION: Use the correct pronoun.
 
 PROMPT: Roberto limpió la cocina.