[vcl] don't manually interfere with compression

Varnish already has [default compression handling](https://varnish-cache.org/docs/trunk/users-guide/compression.html#default-behaviour).
This code only kicks into gear in case of a `miss` or a `pass`, and in
those cases, the backend should be responsible for these.

Author: gquintard

app/code/Magento/PageCache/etc/varnish4.vcl

@@ -76,21 +76,6 @@ sub vcl_recv {
     # collect all cookies
     std.collect(req.http.Cookie);
 
-    # Compression filter. See https://www.varnish-cache.org/trac/wiki/FAQ/Compression
-    if (req.http.Accept-Encoding) {
-        if (req.url ~ "\.(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|ogg|swf|flv)$") {
-            # No point in compressing these
-            unset req.http.Accept-Encoding;
-        } elsif (req.http.Accept-Encoding ~ "gzip") {
-            set req.http.Accept-Encoding = "gzip";
-        } elsif (req.http.Accept-Encoding ~ "deflate" && req.http.user-agent !~ "MSIE") {
-            set req.http.Accept-Encoding = "deflate";
-        } else {
-            # unknown algorithm
-            unset req.http.Accept-Encoding;
-        }
-    }
-
     # Remove all marketing get parameters to minimize the cache objects
     if (req.url ~ "(\?|&)(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=") {
         set req.url = regsuball(req.url, "(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=[-_A-z0-9+()%.]+&?", "");

app/code/Magento/PageCache/etc/varnish5.vcl

@@ -77,21 +77,6 @@ sub vcl_recv {
     # collect all cookies
     std.collect(req.http.Cookie);
 
-    # Compression filter. See https://www.varnish-cache.org/trac/wiki/FAQ/Compression
-    if (req.http.Accept-Encoding) {
-        if (req.url ~ "\.(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|ogg|swf|flv)$") {
-            # No point in compressing these
-            unset req.http.Accept-Encoding;
-        } elsif (req.http.Accept-Encoding ~ "gzip") {
-            set req.http.Accept-Encoding = "gzip";
-        } elsif (req.http.Accept-Encoding ~ "deflate" && req.http.user-agent !~ "MSIE") {
-            set req.http.Accept-Encoding = "deflate";
-        } else {
-            # unknown algorithm
-            unset req.http.Accept-Encoding;
-        }
-    }
-
     # Remove all marketing get parameters to minimize the cache objects
     if (req.url ~ "(\?|&)(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=") {
         set req.url = regsuball(req.url, "(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=[-_A-z0-9+()%.]+&?", "");

app/code/Magento/PageCache/etc/varnish6.vcl

@@ -81,21 +81,6 @@ sub vcl_recv {
     # collect all cookies
     std.collect(req.http.Cookie);
 
-    # Compression filter. See https://www.varnish-cache.org/trac/wiki/FAQ/Compression
-    if (req.http.Accept-Encoding) {
-        if (req.url ~ "\.(jpg|jpeg|png|gif|gz|tgz|bz2|tbz|mp3|ogg|swf|flv)$") {
-            # No point in compressing these
-            unset req.http.Accept-Encoding;
-        } elsif (req.http.Accept-Encoding ~ "gzip") {
-            set req.http.Accept-Encoding = "gzip";
-        } elsif (req.http.Accept-Encoding ~ "deflate" && req.http.user-agent !~ "MSIE") {
-            set req.http.Accept-Encoding = "deflate";
-        } else {
-            # unknown algorithm
-            unset req.http.Accept-Encoding;
-        }
-    }
-
     # Remove all marketing get parameters to minimize the cache objects
     if (req.url ~ "(\?|&)(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=") {
         set req.url = regsuball(req.url, "(gclid|cx|ie|cof|siteurl|zanpid|origin|fbclid|mc_[a-z]+|utm_[a-z]+|_bta_[a-z]+)=[-_A-z0-9+()%.]+&?", "");