Upgrade stringio to 3.0.8 to make sure guides CI pass

Gemfile

@@ -169,12 +169,6 @@ platforms :jruby do
   end
 end
 
-platforms :rbx do
-  # The rubysl-yaml gem doesn't ship with Psych by default as it needs
-  # libyaml that isn't always available.
-  gem "psych", "~> 3.0"
-end
-
 # Gems that are necessary for Active Record tests with Oracle.
 if ENV["ORACLE_ENHANCED"]
   platforms :ruby do

Gemfile.lock

@@ -390,7 +390,8 @@ GEM
       activesupport (>= 7.0.0)
       rack
       railties (>= 7.0.0)
-    psych (3.3.4)
+    psych (5.1.0)
+      stringio
     public_suffix (5.0.1)
     puma (6.0.2)
       nio4r (~> 2.0)
@@ -417,7 +418,8 @@ GEM
     rb-inotify (0.10.1)
       ffi (~> 1.0)
     rbtree (0.4.6)
-    rdoc (6.3.3)
+    rdoc (6.5.0)
+      psych (>= 4.0.0)
     readline-ext (0.1.5)
     redcarpet (3.2.3)
     redis (4.8.0)
@@ -475,7 +477,7 @@ GEM
     rubyzip (2.3.2)
     rufus-scheduler (3.8.2)
       fugit (~> 1.1, >= 1.1.6)
-    sdoc (2.6.0)
+    sdoc (2.6.1)
       rdoc (>= 5.0)
     selenium-webdriver (4.11.0)
       rexml (~> 3.2, >= 3.2.5)
@@ -525,6 +527,7 @@ GEM
     stackprof (0.2.23)
     stimulus-rails (1.2.1)
       railties (>= 6.0.0)
+    stringio (3.0.8)
     sucker_punch (3.1.0)
       concurrent-ruby (~> 1.0)
     tailwindcss-rails (2.0.21)
@@ -612,7 +615,6 @@ DEPENDENCIES
   nokogiri (>= 1.8.1, != 1.11.0)
   pg (~> 1.3)
   propshaft (>= 0.1.7)
-  psych (~> 3.0)
   puma (>= 5.0.3)
   que (< 2)
   queue_classic!