Fix detection of headers values changing

[Nmishin]

Fixes #1885

[github-actions]

changelog detected ✅

[Nmishin]

This fix for: #1885

[jacobbednarz]

added an acceptance test to confirm this behaviour and they are all looking green

TF_ACC=1 go test $(go list ./...) -v -run "^TestAccCloudflareLoadBalancerMonitor_" -count 1 -parallel 1 -timeout 120m -parallel 1
?       github.com/cloudflare/terraform-provider-cloudflare     [no test files]
=== RUN   TestAccCloudflareLoadBalancerMonitor_Import
=== PAUSE TestAccCloudflareLoadBalancerMonitor_Import
=== RUN   TestAccCloudflareLoadBalancerMonitor_Basic
--- PASS: TestAccCloudflareLoadBalancerMonitor_Basic (8.16s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_FullySpecified
--- PASS: TestAccCloudflareLoadBalancerMonitor_FullySpecified (7.96s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_EmptyExpectedBody
--- PASS: TestAccCloudflareLoadBalancerMonitor_EmptyExpectedBody (8.36s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_TcpFullySpecified
--- PASS: TestAccCloudflareLoadBalancerMonitor_TcpFullySpecified (8.63s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_PremiumTypes
--- PASS: TestAccCloudflareLoadBalancerMonitor_PremiumTypes (20.33s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_NoRequired
--- PASS: TestAccCloudflareLoadBalancerMonitor_NoRequired (3.29s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_Update
--- PASS: TestAccCloudflareLoadBalancerMonitor_Update (13.70s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_CreateAfterManualDestroy
--- PASS: TestAccCloudflareLoadBalancerMonitor_CreateAfterManualDestroy (17.04s)
=== RUN   TestAccCloudflareLoadBalancerMonitor_ChangingHeadersCauseReplacement
--- PASS: TestAccCloudflareLoadBalancerMonitor_ChangingHeadersCauseReplacement (15.16s)
=== CONT  TestAccCloudflareLoadBalancerMonitor_Import
--- PASS: TestAccCloudflareLoadBalancerMonitor_Import (9.45s)
PASS
ok      github.com/cloudflare/terraform-provider-cloudflare/internal/provider   112.340s
?       github.com/cloudflare/terraform-provider-cloudflare/version     [no test files]

[github-actions]

This functionality has been released in v3.24.0 of the Terraform Cloudflare Provider.

Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!