Arm backend: Bump cortex-m size test threshold (pytorch#11520)

Size to runtime has grown and this started to fail after some code was
improved/added in the "Refactor FlatTensor" change:
pytorch#11499 and we got ~50 Bytes
over the limit.

Signed-off-by: Zingo Andersen <[email protected]>

Author: zingo

.github/workflows/trunk.yml

@@ -262,7 +262,7 @@ jobs:
         output=$(ls -la ${elf})
         arr=($output)
         size=${arr[4]}
-        threshold="103068" # ~100KiB
+        threshold="103268" # ~100KiB
         echo "size: $size, threshold: $threshold"
         if [[ "$size" -le "$threshold" ]]; then
           echo "Success $size <= $threshold"