Fix dat.ttl_seconds default value mismatch in documentation

[Annu881]

Fixes #11921

Describe changes proposed in this pull request.
Fixes documentation mismatch for dat.ttl_seconds: documented default was 2592000 (30 days) while actual implementation uses -1.

Updated the following documentation files to reflect the correct default value of -1:

• docs/deployment/authorization-and-authentication/Authenticating-Users-via-Tokens.md

• docs/deployment/customization/security.properties-Reference.md

• src/main/resources/security.properties.EXAMPLE
  Code references showing actual default value:

    UidDataAccessTokenServiceImpl.java:59
   @Value("${dat.ttl_seconds:-1}")
  
  JwtUtils.java:80
  @Value("${dat.ttl_seconds:-1}")
  

Checks

• [ x ] The commit log is comprehensible. It follows 7 rules of great commit messages. We can fix this during merge by using a squash+merge if necessary
• Has tests or has a separate issue that describes the types of test that should be created. If no test is included it should explicitly be mentioned in the PR why there is no test.
• Is this PR adding logic based on one or more clinical attributes? If yes, please make sure validation for this attribute is also present in the data validation / data loading layers (in backend repo) and documented in File-Formats Clinical data section!
• Make sure your PR has one of the labels defined in https://github.com/cBioPortal/cbioportal/blob/master/.github/release-drafter.yml

Any screenshots or GIFs?

Not applicable - documentation-only change

Notify reviewers

@inodb @dippindots @mavwolverine

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
75.0% Coverage on New Code
0.0% Duplication on New Code

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