I see now. The problem is as I suspected. The #include directive for DHT.h brings in the dht sensor library, which in turn has an #include directive for a file named Adafruit_Sensor.h. The intended library for that file is the Adafruit Unified Sensor library. However, earlier today a new 3rd party library was installed to the Arduino Web Editor named BNO055SimplePacketComs. That library just so happens to contain a file named Adafruit_Sensor.h. For some reason, the Arduino Web Editor now decides to use the BNO055SimplePacketComs library instead of the Adafruit Unified Sensor library. The BNO055SimplePacketComs library in turn uses another library that requires the Standard Template Library, which is not part of the Uno's toolchain. That causes the error you encountered.
The solution to the problem is to force the Arduino Web Editor to give preference to the Adafruit Unified Sensor library over the BNO055SimplePacketComs library. The way to do this is to import the Adafruit Unified Sensor library as one of your "custom" libraries:
- Download the latest release of the Adafruit Unified Sensor library: https://github.com/adafruit/Adafruit_Sensor/archive/1.0.2.zip
- In the Arduino Web Editor, click the "Libraries" tab.
- Click the import icon (looks like a box with an upward pointing arrow).
- If you get a message about importing your sketchbook, click "Import".
- Select the downloaded Adafruit Unified Sensor library file.
- Click "Open".
- Wait until you get a popup that says the library was successfully imported.