Update current maintainer information

Author: GrahamCampbell

.github/FUNDING.yml

@@ -1 +1 @@
-github: [GrahamCampbell, m1guelpf]
+github: [GrahamCampbell]

.github/SECURITY.md

@@ -9,7 +9,6 @@ are multiple supported versions at any given time.
 ## Reporting a Vulnerability
 
 If you discover a security vulnerability within this package, please send an
-email to Graham Campbell at graham@alt-three.com or Miguel Piedrafita at
-github@miguelpiedrafita.com. All security vulnerabilities will be promptly
-addressed. Please do not disclose security-related issues publicly until a fix
-has been announced.
+email to Graham Campbell at graham@alt-three.com. All security vulnerabilities
+will be promptly addressed. Please do not disclose security-related issues
+publicly until a fix has been announced.

README.md

@@ -110,7 +110,7 @@ $ make test
 
 ## Security
 
-If you discover a security vulnerability within this package, please send an email to Graham Campbell at graham@alt-three.com or Miguel Piedrafita at github@miguelpiedrafita.com. All security vulnerabilities will be promptly addressed. You may view our full security policy [here](https://github.com/GitLabPHP/Client/security/policy).
+If you discover a security vulnerability within this package, please send an email to Graham Campbell at graham@alt-three.com. All security vulnerabilities will be promptly addressed. You may view our full security policy [here](https://github.com/GitLabPHP/Client/security/policy).
 
 
 ## License