fix(sts): stop double-parsing assume_role session tags input

tags was declared as a 'json' block input, so the generic executor
JSON.parse'd it before the switch-case handler ran — but that handler
already converts the raw table-rows array (or a passthrough string)
into the JSON string the sts_assume_role contract expects. Declaring
it 'json' broke that conversion for non-string inputs. Reverted to
'string' so the handler's existing string/array disambiguation runs
on the untouched raw value.

Author: waleedlatif1

apps/sim/blocks/blocks/sts.ts

@@ -356,7 +356,7 @@ export const STSBlock: BlockConfig<STSBaseResponse> = {
     durationSeconds: { type: 'string', description: 'Session duration in seconds' },
     policy: { type: 'string', description: 'JSON IAM session policy to restrict permissions' },
     policyArns: { type: 'string', description: 'Comma-separated managed policy ARNs' },
-    tags: { type: 'json', description: 'Session tags (Key/Value pairs) for ABAC' },
+    tags: { type: 'string', description: 'Session tags (Key/Value pairs) for ABAC' },
     transitiveTagKeys: {
       type: 'string',
       description: 'Comma-separated tag keys that propagate through role chaining',