Remove SAST_EXCLUDED_PATHS from SAST CI template

Why are we doing this work

A bug(#479820 (closed)) caused Semgrep jobs to scan files already handled by GLAS when SEP was configured.

This happened because the customization of SAST_EXCLUDED_PATHS in the SAST CI template was overridden by the default SEP value, more details.

To fix this, we introduced a new variable, SAST_SEMGREP_EXCLUDED_PATHS, in the SAST CI template.

To avoid a regression in the Semgrep analyzer, we should not remove SAST_EXCLUDED_PATHS until the %19.0 when we release a major version of the analyzer.

Relevant links

In Scan Execution Policies, Semgrep also scans ... (#479820 - closed)

Implementation plan

1. In %19.0, remove the following lines (added in !202167 (merged)) from both SAST.gitlab-ci.yml and SAST.latest.gitlab-ci.yml

   # Customization of SAST_EXCLUDED_PATHS to be removed in 19.0, more details <todo add issue link>
   SAST_EXCLUDED_PATHS: "$DEFAULT_SAST_EXCLUDED_PATHS, **/*.py, **/*.go, **/*.java, **/*.js, **/*.jsx, **/*.ts, **/*.tsx, **/*.cjs, **/*.mjs, **/*.cs, **/*.rb, **/*.php"