upgrade xgs SAI to 8.4.39.2 (sonic-net#17842)

Why I did it
Upgrade the xgs SAI version to 8.4.39.2 to include the following fix:

8.4.36.0: [submodule upgrade] [SAI_BRANCH rel_ocp_sai_8_4] SID: SDK-381039 Cosq control dynamic type changes
8.4.37.0: SID: MMU cosq control configuration with Dynamic Type Check
8.4.38.0: [sbumodule upgrade] [CSP 0001232212][SAI_BRANCH rel_ocp_sai_8_4]back-porting SONIC-82415 to SAI 8.4
8.4.39.0: [CSP CS00012320979] Port SONIC-81867 sai spec compliance for get SAI_SWITCH_ATTR_SWITCH_HARDWARE_INFO
8.4.39.1: changes for phy-re-init of 40G ports for TH platforms CS00012327470
8.4.39.2: fix capability for Hostif queue by change SET operation of SAI_HOSTIF_ATTR_QUEUE to be true
Work item tracking
Microsoft ADO (number only): 26491005
How I did it
Upgrade xgs SAI version in sai.mk file.

How to verify it
Run basic SONiC test using SAI release pipeline, all cases passed.
https://dev.azure.com/mssonic/internal/_build/results?buildId=457869&view=results

platform/broadcom/sai.mk

@@ -1,4 +1,4 @@
-LIBSAIBCM_XGS_VERSION = 8.4.35.0
+LIBSAIBCM_XGS_VERSION = 8.4.39.2
 LIBSAIBCM_DNX_VERSION = 9.2.12.1
 LIBSAIBCM_XGS_BRANCH_NAME = SAI_8.4.0_GA
 LIBSAIBCM_DNX_BRANCH_NAME = SAI_9.2.0.3