html-proofer: Update the dependencies (security, CVE-2020-7595)

This updates nokogiri to 1.10.8 for CVE-2020-7595 [0].

[0]: https://github.com/sparklemotion/nokogiri/issues/1992

pkgs/tools/misc/html-proofer/Gemfile.lock

@@ -5,7 +5,7 @@ GEM
       public_suffix (>= 2.0.2, < 5.0)
     ethon (0.12.0)
       ffi (>= 1.3.0)
-    ffi (1.12.1)
+    ffi (1.12.2)
     html-proofer (3.15.1)
       addressable (~> 2.3)
       mercenary (~> 0.3)
@@ -16,7 +16,7 @@ GEM
       yell (~> 2.0)
     mercenary (0.4.0)
     mini_portile2 (2.4.0)
-    nokogiri (1.10.7)
+    nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
     nokogumbo (2.0.2)
       nokogiri (~> 1.8, >= 1.8.4)
@@ -25,7 +25,7 @@ GEM
     rainbow (3.0.0)
     typhoeus (1.3.1)
       ethon (>= 0.9.0)
-    yell (2.2.1)
+    yell (2.2.2)
 
 PLATFORMS
   ruby