patch 8.2.3525: option variable name does not match option name

Problem:    Option variable name does not match option name. (Christ van
            Willigen)
Solution:   Rename the variable.
diff --git a/src/insexpand.c b/src/insexpand.c
index 624146a..bcaa3fd 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -301,7 +301,7 @@
 							)
 		 : (*curbuf->b_p_tsr == NUL && *p_tsr == NUL
 #ifdef FEAT_COMPL_FUNC
-		     && *curbuf->b_p_thsfu == NUL
+		     && *curbuf->b_p_tsrfu == NUL
 #endif
 		   ))
     {
@@ -2246,7 +2246,7 @@
 	case CTRL_X_OMNI:
 	    return curbuf->b_p_ofu;
 	case CTRL_X_THESAURUS:
-	    return curbuf->b_p_thsfu;
+	    return curbuf->b_p_tsrfu;
 	default:
 	    return (char_u *)"";
     }
@@ -2751,8 +2751,8 @@
 {
 #ifdef FEAT_COMPL_FUNC
     return (type == CTRL_X_THESAURUS
-		&& curbuf->b_p_thsfu != NULL
-		&& *curbuf->b_p_thsfu != NUL);
+		&& curbuf->b_p_tsrfu != NULL
+		&& *curbuf->b_p_tsrfu != NUL);
 #else
     return FALSE;
 #endif