fix: add timezone to date string

[BlairCurrey]

Changes proposed in this pull request

• add 'Z' to date string

Context

fixes #3906

Checklist

• Related issues linked using fixes #number
• Tests added/updated
• Make sure that all checks pass
• Bruno collection updated (if necessary)
• Documentation issue created with user-docs label (if necessary)
• OpenAPI specs updated (if necessary)

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[github-actions]

🚀 Performance Test Results

Test Configuration:

• VUs: 4
• Duration: 1m0s

Test Metrics:

• Requests/s: 51.00
• Iterations/s: 16.99
• Failed Requests: 0.00% (0 of 3067)

📜 Logs

> performance@1.0.0 run-tests:testenv /home/runner/work/rafiki/rafiki/test/performance
> ./scripts/run-tests.sh -e test "-k" "-q" "--vus" "4" "--duration" "1m"

Cloud Nine GraphQL API is up: http://localhost:3101/graphql
Cloud Nine Wallet Address is up: http://localhost:3100/
Happy Life Bank Address is up: http://localhost:4100/
cloud-nine-wallet-test-backend already set
cloud-nine-wallet-test-auth already set
happy-life-bank-test-backend already set
happy-life-bank-test-auth already set
     data_received..................: 1.1 MB 18 kB/s
     data_sent......................: 2.4 MB 39 kB/s
     http_req_blocked...............: avg=6.41µs   min=1.77µs   med=5.15µs   max=1.22ms   p(90)=6.41µs   p(95)=6.97µs  
     http_req_connecting............: avg=250ns    min=0s       med=0s       max=230.87µs p(90)=0s       p(95)=0s      
     http_req_duration..............: avg=77.82ms  min=7.16ms   med=61.71ms  max=407.51ms p(90)=130.65ms p(95)=154.28ms
       { expected_response:true }...: avg=77.82ms  min=7.16ms   med=61.71ms  max=407.51ms p(90)=130.65ms p(95)=154.28ms
     http_req_failed................: 0.00%  ✓ 0         ✗ 3067
     http_req_receiving.............: avg=81.94µs  min=25.5µs   med=73.3µs   max=1.68ms   p(90)=109.24µs p(95)=134.75µs
     http_req_sending...............: avg=33.33µs  min=10.73µs  med=26.37µs  max=1.18ms   p(90)=38.6µs   p(95)=53.36µs 
     http_req_tls_handshaking.......: avg=0s       min=0s       med=0s       max=0s       p(90)=0s       p(95)=0s      
     http_req_waiting...............: avg=77.7ms   min=7.02ms   med=61.61ms  max=407.41ms p(90)=130.56ms p(95)=154.2ms 
     http_reqs......................: 3067   50.996924/s
     iteration_duration.............: avg=235.11ms min=160.29ms med=222.92ms max=758.81ms p(90)=286.88ms p(95)=326.42ms
     iterations.....................: 1022   16.993432/s
     vus............................: 4      min=4       max=4 
     vus_max........................: 4      min=4       max=4