Add a missing closing quote in INSTALLED_RECOVERY_BUILD_PROP_TARGET.

Missing that doesn't seem to affect correctness, but it upsets the
syntax parsing in my editor.

Test: `m -j out/target/product/marlin/recovery/root/prop.default` with
      aosp_marlin-userdebug.
Change-Id: I272f6a6e4fe67b3ef316aa38896a0df0b42228d0