Update tensorflow to 2.12 in requirements.txt

Change-Id: I034049ee8a4bb471e9b57d066e102d08a755d698
Signed-off-by: Jonny Svärd <jonny.svaerd@arm.com>
diff --git a/requirements.txt b/requirements.txt
index e691cf8..57f9897 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
 ethos-u-vela
 pillow
 pyelftools
-tensorflow==2.11
+tensorflow==2.12