Updated C++ and Unity builds to use latest release Cocoapods.

Firebase: 6.13.0
Crashlytics: 3.14.0
Instance ID: 4.2.7

Held GoogleDataTransport, GoogleDataTransportCCTSupport and
FirebaseCoreDiagnostics at previous versions by manually
editing the ios/BUILD file. These pods are currently missing
binary frameworks (iOS team did not update) and are therefore
not possible to build against.

PiperOrigin-RevId: 285873743

Author: smiles

version.sh

@@ -18,9 +18,9 @@
 
 # Used to generate Pod dependencies in the Firebase Unity plugin.
 declare -A POD_SDK_VERSIONS=(
-  ["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.
+  ["released"]="6.13.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
+  ["stable"]="6.13.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
+  ["head"]="6.13.0"  # gen_build.sh: [FIR] Managed by a script. DO NOT EDIT.
 )
 
 help() {