Remove problematic SQL migration to add Icon column to static pages

[juanluisrp]

The column is added automatically by Hibernate when GeoNetwork starts. Removing it
from the SQL because it makes the process to fail with

Duplicate column name "ICON"; SQL statement:
 ALTER TABLE public.spg_page ADD icon varchar NUL [42121-212]

Related to #7536.

Checklist

• I have read the contribution guidelines
• Pull request provided for main branch, backports managed with label
• Good housekeeping of code, cleaning up comments, tests, and documentation
• Clean commit history broken into understandable chucks, avoiding big commits with hundreds of files, cautious of reformatting and whitespace changes
• Clean commit messages, longer verbose messages are encouraged
• API Changes are identified in commit messages
• Testing provided for features or enhancements using automatic tests
• User documentation provided for new features or enhancements in manual
• Build documentation provided for development instructions in README.md files
• Library management using pom.xml dependency management. Update build documentation with intended library use and library tutorials or documentation

[sonarcloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[josegar74]

Tested and works fine.