ota_from_target_files: read correct api level

ro.product.first_api_level looks like the value we actually want to read
to since it inherits from $PRODUCT_SHIPPING_API_LEVEL. Other variables
we attempted to look at were giving other values (e.g 202504 for pixel
watch)

Bug: 331202590
Test: th
Change-Id: Ied3da247cba45611132db6c9e3cdefb447891f96
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 264c2d8..1a7a29d 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -490,7 +490,6 @@
       return -1
 
     props = [
-        "ro.board.api_level",
         "ro.board.first_api_level",
         "ro.product.first_api_level",
     ]