chore: update Go version to 1.25 in config and docs

Bump Go version to 1.25 in GitHub Actions workflow and go.mod. Remove outdated Go version requirement from README.

Author: jferrl

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
       contents: read # for actions/checkout to fetch code
     strategy:
       matrix:
-        go-version: [1.x, 1.24.x]
+        go-version: [1.x, 1.25.x]
         platform: [ubuntu-latest]
         include:
           # only update test coverage stats with the most recent go version on linux

README.md

@@ -29,7 +29,6 @@
 
 ### Requirements
 
-- **Go 1.18+** (required for generics support)
 - This package is designed to be used with the `golang.org/x/oauth2` package
 
 ## Installation

go.mod

@@ -1,6 +1,6 @@
 module github.com/jferrl/go-githubauth
 
-go 1.24.6
+go 1.25
 
 require (
 	github.com/golang-jwt/jwt/v5 v5.3.0