escapeKotlinKeywords = true not using right property name in `toString`

[bjoernmayer]

The Proto

message JwtLocation {
  oneof in {
    string header = 1;
    string query = 2;
    string cookie = 4;
  }

  string value_prefix = 3;
}

with wire config

escapeKotlinKeywords = true 

// And. not sure if this influences this:
oneofMode = "sealed_class"

results in this wrong toString()

override fun toString(): String {
    val result = mutableListOf<String>()
    if (`in` != null) result += """in=$in"""
    result += """value_prefix=${sanitize(value_prefix)}"""
    return result.joinToString(prefix = "JwtLocation{", separator = ", ", postfix = "}")
  }

Should be

override fun toString(): String {
    val result = mutableListOf<String>()
    if (`in` != null) result += """in=$`in`"""
    result += """value_prefix=${sanitize(value_prefix)}"""
    return result.joinToString(prefix = "JwtLocation{", separator = ", ", postfix = "}")
  }