Postgres 13

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CREATE TABLE t (id int, doc jsonb);
INSERT INTO t VALUES 
(1,'{"card": "gold","country": "France","Type of travel": "Business","Company": "KLM"}'::jsonb),
(2,'{"card": "silver","country": "Isle of Man","Type of travel": "Business","Company": "EasyJet"}'::jsonb);

CREATE TABLE

INSERT 0 2

WITH j (id,doc_upper) AS (
  SELECT id,jsonb_object_agg(upper(k),v) FROM t
  CROSS JOIN LATERAL jsonb_each_text(doc) j(k,v)
  GROUP BY id
)
UPDATE t SET doc = j.doc_upper
FROM j WHERE j.id = t.id;

UPDATE 2

SELECT * FROM t

id
doc

1
{"CARD": "gold", "COMPANY": "KLM", "COUNTRY": "France", "TYPE OF TRAVEL": "Business"}

2
{"CARD": "silver", "COMPANY": "EasyJet", "COUNTRY": "Isle of Man", "TYPE OF TRAVEL": "Business"}

SELECT 2

id	doc
1	{"CARD": "gold", "COMPANY": "KLM", "COUNTRY": "France", "TYPE OF TRAVEL": "Business"}
2	{"CARD": "silver", "COMPANY": "EasyJet", "COUNTRY": "Isle of Man", "TYPE OF TRAVEL": "Business"}