Close #12326: sys.platform is now always 'linux' on Linux

On Linux, sys.platform doesn't contain the major version anymore. It is now
always 'linux', instead of 'linux2' or 'linux3' depending on the Linux version
used to build Python.
diff --git a/Misc/NEWS b/Misc/NEWS
index 29a2e6f..a2943a7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -265,6 +265,10 @@
 Library
 -------
 
+- Issue #12326: On Linux, sys.platform doesn't contain the major version
+  anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending
+  on the Linux version used to build Python.
+
 - Issue #12213: Fix a buffering bug with interleaved reads and writes that
   could appear on BufferedRandom streams.