MLBEDSW-4962: Update release notes

This commit contains the release notes
for Vela 3.1.0. It also increases the
PyPI documentation tag.

Signed-off-by: Dwight Lidman <dwight.lidman@arm.com>
Change-Id: Iffd9fac7d4a7ccb34c3558990ef4bb97e548bf4c
diff --git a/setup.py b/setup.py
index 2aa23ca..50fd506 100644
--- a/setup.py
+++ b/setup.py
@@ -40,7 +40,7 @@
 this_directory = os.path.abspath(os.path.dirname(__file__))
 with open(os.path.join(this_directory, "README.md"), encoding="utf-8") as f:
     long_description = f.read()
-    tag = "3.0.0"
+    tag = "3.1.0"
     url = f"https://review.mlplatform.org/plugins/gitiles/ml/ethos-u/ethos-u-vela/+/refs/tags/{tag}/"
     # Find all markdown links that match the format:  [text](link)
     for match, link in re.findall(r"(\[.+?\]\((.+?)\))", long_description):