docs: fix malformed link in SECURITY.md reporting instructions

The "instructions" link contained a nested, duplicated URL
(`[instructions]([url](URL)URL)`) that rendered broken. Correct it to a
normal `[instructions](URL)` pointing at GitHub's private
vulnerability-reporting guide.

Co-Authored-By: Claude <noreply@anthropic.com>
Ref: EC-2134

Author: robnester-rh

SECURITY.md

@@ -9,7 +9,7 @@
 ## Reporting a Vulnerability
 
 To report a security issue, please click on the "Report a vulnerability" button from the "Security" tab.
-See detailed [instructions]([url](https://docs.github.com/en/code-security/security-advisories/guidance-on-reporting-and-writing/privately-reporting-a-security-vulnerability#privately-reporting-a-security-vulnerability)https://docs.github.com/en/code-security/security-advisories/guidance-on-reporting-and-writing/privately-reporting-a-security-vulnerability#privately-reporting-a-security-vulnerability).
+See detailed [instructions](https://docs.github.com/en/code-security/security-advisories/guidance-on-reporting-and-writing/privately-reporting-a-security-vulnerability#privately-reporting-a-security-vulnerability).
 
 The maintainers will respond within 3 working days of the report.
 If the issue is confirmed as a vulnerability, we will open a Security Advisory.