opentelemetry-exporter-prometheus-remote-write: workaround build failure with PyPy 3.8 (open-telemetry#3480)

Find a version that has a wheel for PyPy 3.8 skipping the failing test
while we bump the baseline to 3.9.

Author: xrmx

exporter/opentelemetry-exporter-prometheus-remote-write/test-requirements.txt

@@ -2,7 +2,7 @@ asgiref==3.8.1
 certifi==2024.7.4
 charset-normalizer==3.3.2
 # We can drop this after bumping baseline to pypy-39
-cramjam==2.1.0; platform_python_implementation == "PyPy"
+cramjam==2.8.0; platform_python_implementation == "PyPy"
 cramjam==2.8.4; platform_python_implementation != "PyPy"
 Deprecated==1.2.14
 idna==3.7

exporter/opentelemetry-exporter-prometheus-remote-write/tests/test_prometheus_remote_write_exporter.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import unittest
+from platform import python_implementation
 from unittest.mock import patch
 
 import pytest
@@ -282,6 +283,10 @@ def test_invalid_tls_config_key_only_param(self):
             )
 
 
+@pytest.mark.skipif(
+    python_implementation() == "PyPy",
+    reason="Fails with pypy 3.8, bump cramjam when 3.9 is baseline",
+)
 # Ensures export is successful with valid export_records and config
 @patch("requests.post")
 def test_valid_export(mock_post, prom_rw, metric):