[oracle-database] Update release information

[etil2jz]

On October 14th, Oracle decided to replace 23ai with the new 26ai release, vanishing mentions of 23ai in their documentation.

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[usta]

@etil2jz why do you want to remove 23 cycle ? And we are NOT allowing to add future ( not released ) versions as PR

[marcwrobel]

Given what's said on https://mikedietrichde.com/2025/10/14/oracle-ai-database-26ai-replaces-oracle-database-23ai/, we can either:

1. replace also 23ai with 26ai as suggested, add a note in the description to explain what happened, and set up a redirect, as suggested in this PR,
2. or add a new 26ai release cycle, deprecating the 23ai, and add a note in the description to explain what happened.

I would prefer the 2nd solution : it is not a breaking change, and it makes more obvious what happened.

@etil2jz are you willing to perform those changes in this PR ?