style: no capitalized error messages

pkg/parser/parser.go

@@ -74,7 +74,7 @@ func ParseExpression(i *iterator.Iterator[tokenizer.Token]) (lambda.Expression,
 
 		close, closeErr := i.Next()
 		if closeErr != nil {
-			return nil, fmt.Errorf("Could not parse call terminating parenthesis: %w", closeErr)
+			return nil, fmt.Errorf("could not parse call terminating parenthesis: %w", closeErr)
 		} else if close.Type != tokenizer.TokenCloseParen {
 			return nil, fmt.Errorf("expected call terminating parenthesis, got '%v' (column %v)", close.Value, close.Index)
 		}