Reformat some Go files

When working on #994 I noticed that some Go files are not formatted with
`gofmt`.

This PR fixes this.

reader/rewrite/rewrite_functions.go

@@ -229,4 +229,3 @@ func replaceCustom(entryContent string, searchTerm string, replaceTerm string) s
 	}
 	return entryContent
 }
-

reader/rewrite/rewriter.go

@@ -5,8 +5,8 @@
 package rewrite // import "miniflux.app/reader/rewrite"
 
 import (
-	"strings"
 	"regexp"
+	"strings"
 
 	"miniflux.app/logger"
 	"miniflux.app/url"

ui/login_show.go

@@ -7,8 +7,8 @@ package ui // import "miniflux.app/ui"
 import (
 	"net/http"
 
-	"miniflux.app/http/response/html"
 	"miniflux.app/http/request"
+	"miniflux.app/http/response/html"
 	"miniflux.app/http/route"
 	"miniflux.app/ui/session"
 	"miniflux.app/ui/view"

ui/oauth2.go

@@ -6,6 +6,7 @@ package ui // import "miniflux.app/ui"
 
 import (
 	"context"
+
 	"miniflux.app/config"
 	"miniflux.app/oauth2"
 )