[submodule] Advance sonic-swss-common pointer

Update sonic-swss-common submodule pointer to include the following:

* 6e4daf1 Revamp module build script to make it work for 5.15 on Ubuntu 20.04 (sonic-net/sonic-swss-common#720)
* 7f40cde Non recursive automake and Debian packaging changes (sonic-net/sonic-swss-common#700)

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

rules/swss-common.mk

@@ -27,7 +27,7 @@ endif
 PYTHON3_SWSSCOMMON = python3-swsscommon_$(LIBSWSSCOMMON_VERSION)_$(CONFIGURED_ARCH).deb
 $(eval $(call add_derived_package,$(LIBSWSSCOMMON),$(PYTHON3_SWSSCOMMON)))
 
-LIBSWSSCOMMON_DBG = $(LIBSWSSCOMMON_NAME)-dbg_$(LIBSWSSCOMMON_VERSION)_$(CONFIGURED_ARCH).deb
+LIBSWSSCOMMON_DBG = $(LIBSWSSCOMMON_NAME)-dbgsym_$(LIBSWSSCOMMON_VERSION)_$(CONFIGURED_ARCH).deb
 $(LIBSWSSCOMMON_DBG)_DEPENDS += $(LIBSWSSCOMMON)
 $(LIBSWSSCOMMON_DBG)_RDEPENDS += $(LIBSWSSCOMMON)
 $(eval $(call add_derived_package,$(LIBSWSSCOMMON),$(LIBSWSSCOMMON_DBG)))