Remove obsolete cd at the end of a component

This is no longer useful now that components run in a subshell.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index d70ed77..24fc27d 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -2996,15 +2996,10 @@
 
 component_test_cmake_as_subdirectory () {
     msg "build: cmake 'as-subdirectory' build"
-    MBEDTLS_ROOT_DIR="$PWD"
-
     cd programs/test/cmake_subproject
     cmake .
     make
     ./cmake_subproject
-
-    cd "$MBEDTLS_ROOT_DIR"
-    unset MBEDTLS_ROOT_DIR
 }
 support_test_cmake_as_subdirectory () {
     support_test_cmake_out_of_source