payloads/edk2: Update default branch for MrChromebox repo to 2023-06

Update the default branch used for MrChromebox's edk2 fork from 2023-04
to 2023-06. This updated branch has been rebased on the latest upstream
stable tag (edk2-stable202305), and fixes issues booting on AMD Zen
platforms (Picasso and newer).

TEST=build/boot google boards link, panther, lulu,reef, ampton, akemi,
banshee, zork, frostflow with edk2 payload selected.

Change-Id: I4867d453514f2b00f66ffdad50e091e5b80afdcb
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76806
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
diff --git a/payloads/external/edk2/Kconfig b/payloads/external/edk2/Kconfig
index 1057c43..ddc521c 100644
--- a/payloads/external/edk2/Kconfig
+++ b/payloads/external/edk2/Kconfig
@@ -81,7 +81,7 @@
 
 config EDK2_TAG_OR_REV
 	string "Insert a commit's SHA-1 or a branch name"
-	default "origin/uefipayload_202304" if EDK2_REPO_MRCHROMEBOX
+	default "origin/uefipayload_202306" if EDK2_REPO_MRCHROMEBOX
 	default "origin/universalpayload" if EDK2_UNIVERSAL_PAYLOAD
 	default "origin/master" if EDK2_REPO_OFFICIAL
 	default "" if EDK2_REPO_CUSTOM