Update iOS Pods version for M59 6.8.0

Manually override version due to missing framework.
  GoogleDataTransport from 3.1.0 to 3.0.1
  FirebaseMessaging from 4.1.9 to 4.1.8
  FirebaseAuth from 6.4.0 to 6.3.1
  FirebaseStorage from 3.4.2 to 3.4.1
  FirebasePerformance from 3.1.7 to 3.1.6
  FirebaseRemoteConfig from 4.4.5 to 4.4.4
  FirebaseCoreDiagnostics from 1.1.2 to 1.1.1
  GoogleDataTransportCCTSupport from 1.2.2 to 1.2.1

PiperOrigin-RevId: 281633499

Author: chkuang-g

version.sh

@@ -18,9 +18,9 @@
 
 # Used to generate Pod dependencies in the Firebase Unity plugin.
 declare -A POD_SDK_VERSIONS=(
-  ["released"]="6.10.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
-  ["stable"]="6.10.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
-  ["head"]="6.10.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
+  ["released"]="6.12.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
+  ["stable"]="6.12.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
+  ["head"]="6.12.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
 )
 
 help() {