Remove -mod=vendor from all documentation and code

helpers/build-release-binaries/main.go

@@ -96,7 +96,6 @@ func build(sourceDir, outputDir, goos, goarch string) (filename string) {
 	outputFile := filepath.Join(outputDir, filename)
 
 	c := exec.Command("go", "build",
-		"-mod=vendor",
 		"-o", outputFile,
 		"-ldflags", "-s -w",
 		"-tags", "selfupdate",

helpers/prepare-release/main.go

@@ -345,7 +345,7 @@ func runBuild(sourceDir, outputDir, version string) {
 		"--volume", sourceDir+":/restic",
 		"--volume", outputDir+":/output",
 		"restic/builder",
-		"go", "run", "-mod=vendor", "helpers/build-release-binaries/main.go",
+		"go", "run", "helpers/build-release-binaries/main.go",
 		"--version", version)
 }