Fix parser translator edge-case when multiline string ends with \n

lib/prism/translation/parser/compiler.rb

@@ -2144,7 +2144,9 @@ def string_nodes_from_line_continuations(unescaped, escaped, start_offset, openi
               .each do |lines|
                 escaped_lengths << lines.sum(&:bytesize)
                 unescaped_lines_count = lines.sum do |line|
-                  line.scan(/(\\*)n/).count { |(backslashes)| backslashes&.length&.odd? || false }
+                  count = line.scan(/(\\*)n/).count { |(backslashes)| backslashes&.length&.odd? }
+                  count -= 1 if !line.end_with?("\n") && count > 0
+                  count
                 end
                 extra = 1
                 extra = lines.count if percent_array # Account for line continuations in percent arrays

test/prism/fixtures/dstring.txt

@@ -34,5 +34,9 @@ b\nar
 #{}
 "
 
+"foo
+\n#{}bar\n\n#{}
+a\nb\n#{}\nc\n"
+
 "
 ’"

test/prism/fixtures/strings.txt

@@ -45,6 +45,10 @@ foo\
 b\nar
 "
 
+"foo
+\nbar\n\n
+a\nb\n\nc\n"
+
 %q{abc}
 
 %s[abc]