docs: Clarify PyPy support

Author: bkeryan

CHANGELOG.md

@@ -41,6 +41,7 @@ All notable changes to this project will be documented in this file.
           distribution package and affected clients. Adding PyPy-specific constraints exacerbated
           this problem. Now, the distribution package specifies only a lower bound for the `numpy`
           and `click` versions.
+    * Clarify PyPy support and enable unit testing with PyPy.
 
 * ### Known Issues
     * ...

README.rst

@@ -55,7 +55,9 @@ system.
 Python Version Support
 ----------------------
 
-**nidaqmx** supports CPython 3.9+ and PyPy3.
+**nidaqmx** supports CPython 3.9+.
+
+**nidaqmx** supports PyPy3 for non-gRPC use cases.
 
 Installation
 ============