bug: ARDUINO_ARCH_RP2040 does not include the right pgmspace header

[gabrielcsapo]

Thank you for creating a pull request to contribute to Adafruit's GitHub code! Before you open the request please review the following guidelines and tips to help it be more easily integrated:

• Describe the scope of your change--i.e. what the change does and what parts of the code were modified. This will help us understand any risks of integrating the code.

When utilizing this in a project with the RP2040, the following error occurs

fatal error: pgmspace.h: No such file or directory
#include <pgmspace.h>
          ^~~~~~~~~~~~
compilation terminated.

• Describe any known limitations with your change. For example if the change doesn't apply to a supported platform of the library please mention it.

None known.

• Please run any tests or examples that can exercise your modified code. We strive to not break users of the code and running tests/examples helps with this process.

Verified by running this locally on a rp2040. Examples on the esp32 still work as expected.

Thank you again for contributing! We will try to test and integrate the change as soon as we can, but be aware we have many GitHub repositories to manage and can't immediately respond to every request. There is no need to bump or check in on a pull request (it will clutter the discussion of the request).

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After reviewing the guidelines above you can delete this text from the pull request.

[per1234]

Fixes https://github.com/adafruit/Adafruit_SSD1306/issues/259

[mihailShumilov]

Issue still exists - I need this PR