Upgrade xgs SAI version to 10.1.42.0 (#20119)

Why I did it
Upgrade xgs SAI version to 10.1.42.0 with the following fixes.

10.1.39.0: [CSP CS00012349283] back-porting SONIC-88703 to SAI10.1
10.1.40.0: [CSP CS00012352844] port SONIC-92490 to rel_ocp_sai_10_1
10.1.41.0: [CS00012358054] Port SONIC-93029 to 10.1GA. Description: [TH2/TH] Warm reboot from SAI 4.3.5 to SAI 8.4 SONiC image fails
10.1.42.0: [CS00012361544] Backport SONIC-93974 to 10.1. Description: MSFT Prod Issue - TD2 device is sending massive PFC
Work item tracking
Microsoft ADO (number only): 29305413
How I did it
Update xgs SAI version to 10.1.42.0 in sai.mk file.

How to verify it
Run SAI release validation pipeline: https://dev.azure.com/mssonic/internal/_build/results?buildId=632622&view=results

Which release branch to backport (provide reason below if selected)
 202311
 202405

platform/broadcom/sai.mk

@@ -1,4 +1,4 @@
-LIBSAIBCM_XGS_VERSION = 10.1.38.0
+LIBSAIBCM_XGS_VERSION = 10.1.42.0
 LIBSAIBCM_DNX_VERSION = 11.2.7.1
 LIBSAIBCM_XGS_BRANCH_NAME = SAI_10.1.0_GA
 LIBSAIBCM_DNX_BRANCH_NAME = SAI_11.2.0_GA