Remove some engines : subtitleseeker, seedpeer, swisscows

http://www.subtitleseeker.com and http://www.seedpeer.eu don't exist anymore.
https://swisscows.ch/ has change : the engine needs to be updated

searx/settings.yml

@@ -568,24 +568,12 @@ engines:
     engine : spotify
     shortcut : stf
 
-  - name : subtitleseeker
-    engine : subtitleseeker
-    shortcut : ss
-# The language is an option. You can put any language written in english
-# Examples : English, French, German, Hungarian, Chinese...
-#    language : English
-
   - name : startpage
     engine : startpage
     shortcut : sp
     timeout : 6.0
     disabled : True
 
-  - name : swisscows
-    engine : swisscows
-    shortcut : sw
-    disabled : True
-
   - name : tokyotoshokan
     engine : tokyotoshokan
     shortcut : tt
@@ -664,12 +652,6 @@ engines:
     timeout: 6.0
     categories : science
 
-  - name : seedpeer
-    engine : seedpeer
-    shortcut: speu
-    categories: files, music, videos
-    disabled: True
-
   - name : dictzone
     engine : dictzone
     shortcut : dc