Remove the usage of deprecated methods of KeyStoreManager class

[UdeshAthukorala]

Purpose

• Remove the usage of deprecated methods of KeyStoreManager class

Part of: wso2/product-is#21206

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 45.34%. Comparing base (cab60a0) to head (6430089).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...on/identity/sso/saml/admin/SAMLSSOConfigAdmin.java	0.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #438      +/-   ##
============================================
- Coverage     45.36%   45.34%   -0.02%     
+ Complexity     1609     1441     -168     
============================================
  Files           116      116              
  Lines         10226    10225       -1     
  Branches       1305     1298       -7     
============================================
- Hits           4639     4637       -2     
- Misses         4947     4948       +1     
  Partials        640      640              

Flag	Coverage Δ
unit	20.21% <0.00%> (+<0.01%)	⬆️

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