Update Go version in tests to 1.26.0-rc.1

MODULE.bazel

@@ -263,7 +263,7 @@ use_repo(
 )
 
 go_sdk = use_extension("@rules_go//go:extensions.bzl", "go_sdk")
-go_sdk.download(version = "1.25.0")
+go_sdk.download(version = "1.26rc1")
 
 go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps")
 go_deps.from_file(go_mod = "//go/extractor:go.mod")

go/actions/test/action.yml

@@ -4,7 +4,7 @@ inputs:
   go-test-version:
     description: Which Go version to use for running the tests
     required: false
-    default: "~1.25.0"
+    default: "1.26.0-rc.1"
   run-code-checks:
     description: Whether to run formatting, code and qhelp generation checks
     required: false

go/extractor/go.mod

@@ -1,8 +1,8 @@
 module github.com/github/codeql-go/extractor
 
-go 1.25
+go 1.26
 
-toolchain go1.25.0
+toolchain go1.26rc1
 
 // when updating this, run
 //    bazel run @rules_go//go -- mod tidy