SECURITY.md: fix markdown style issues

Fix markdown style issues using markdownlint tool [1]:

$ cat SECURITY.md | mdl
(stdin):16: MD013 Line length
(stdin):19: MD013 Line length
(stdin):20: MD013 Line length
(stdin):1: MD026 Trailing punctuation in header
(stdin):6: MD034 Bare URL used
(stdin):16: MD034 Bare URL used
(stdin):19: MD034 Bare URL used

[1] https://github.com/markdownlint/markdownlint
(From OE-Core rev: 5339f5988afce79e9ff56788f715671579fd7cd1)

Signed-off-by: Igor Opaniuk <igor.opaniuk@foundries.io>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

SECURITY.md

@@ -1,9 +1,9 @@
-How to Report a Potential Vulnerability?
-========================================
+How to Report a Potential Vulnerability
+=======================================
 
 If you would like to report a public issue (for example, one with a released
 CVE number), please report it using the
-[https://bugzilla.yoctoproject.org/enter_bug.cgi?product=Security Security Bugzilla]
+[Security Bugzilla](https://bugzilla.yoctoproject.org/enter_bug.cgi?product=Security)
 
 If you are dealing with a not-yet released or urgent issue, please send a
 message to security AT yoctoproject DOT org, including as many details as
@@ -13,10 +13,10 @@ and any example code, if available.
 Branches maintained with security fixes
 ---------------------------------------
 
-See [https://wiki.yoctoproject.org/wiki/Stable_Release_and_LTS Stable release and LTS]
+See [Stable release and LTS](https://wiki.yoctoproject.org/wiki/Stable_Release_and_LTS)
 for detailed info regarding the policies and maintenance of Stable branches.
 
-The [https://wiki.yoctoproject.org/wiki/Releases Release page] contains a list of all
-releases of the Yocto Project. Versions in grey are no longer actively maintained with
-security patches, but well-tested patches may still be accepted for them for
-significant issues.
+The [Release page](https://wiki.yoctoproject.org/wiki/Releases) contains
+a list of all releases of the Yocto Project. Versions in grey are no longer
+actively maintained with security patches, but well-tested patches may still
+be accepted for them for significant issues.