Remove non-portable shell builtin local

Dash and bash have `local`, but other sh implementations such as ksh
don't.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 0587323..909320e 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -951,7 +951,7 @@
 run_test_memory_after_hanshake_with_mfl()
 {
     # The test passes if the difference is around 2*(16k-MFL)
-    local MEMORY_USAGE_LIMIT="$(( $2 - ( 2 * ( 16384 - $1 )) ))"
+    MEMORY_USAGE_LIMIT="$(( $2 - ( 2 * ( 16384 - $1 )) ))"
 
     # Leave some margin for robustness
     MEMORY_USAGE_LIMIT="$(( ( MEMORY_USAGE_LIMIT * 110 ) / 100 ))"