fix: Update jekyll-last-modified-at for Apple silicon builds

* posix-spawn v0.3.15 was introducing build errors on Apple silicon machine
  installs. Updating jekyll-last-modified-at, which had previously required
  posix-spawn drops the dependency and the install and build then works.
   - Updated via 'bundle update jekyll-last-modified-at'.

Gemfile.lock

@@ -1,19 +1,19 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.8.1)
-      public_suffix (>= 2.0.2, < 6.0)
+    addressable (2.8.7)
+      public_suffix (>= 2.0.2, < 7.0)
     ast (2.4.2)
     colorator (1.1.0)
-    concurrent-ruby (1.1.10)
+    concurrent-ruby (1.3.3)
     diff-lcs (1.5.0)
     em-websocket (0.5.3)
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0)
     ethon (0.16.0)
       ffi (>= 1.15.0)
     eventmachine (1.2.7)
-    ffi (1.15.5)
+    ffi (1.17.0)
     forwardable-extended (2.6.0)
     html-proofer (4.4.3)
       addressable (~> 2.3)
@@ -25,7 +25,7 @@ GEM
       yell (~> 2.0)
       zeitwerk (~> 2.5)
     http_parser.rb (0.8.0)
-    i18n (1.12.0)
+    i18n (1.14.5)
       concurrent-ruby (~> 1.0)
     jekyll (4.2.2)
       addressable (~> 2.4)
@@ -48,9 +48,8 @@ GEM
       jekyll (>= 3.7, < 5.0)
     jekyll-indico (0.6.2)
       jekyll (>= 3.8, < 5.0)
-    jekyll-last-modified-at (1.3.0)
+    jekyll-last-modified-at (1.3.2)
       jekyll (>= 3.7, < 5.0)
-      posix-spawn (~> 0.3.9)
     jekyll-sass-converter (2.2.0)
       sassc (> 2.0.1, < 3.0)
     jekyll-seo-tag (2.8.0)
@@ -61,8 +60,8 @@ GEM
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)
-    liquid (4.0.3)
-    listen (3.7.1)
+    liquid (4.0.4)
+    listen (3.9.0)
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.4.0)
@@ -84,16 +83,15 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     pkg-config (1.5.1)
-    posix-spawn (0.3.15)
-    public_suffix (5.0.1)
+    public_suffix (6.0.1)
     racc (1.7.3)
     rainbow (3.1.1)
     rake (13.0.6)
     rb-fsevent (0.11.2)
-    rb-inotify (0.10.1)
+    rb-inotify (0.11.1)
       ffi (~> 1.0)
     regexp_parser (2.6.1)
-    rexml (3.3.3)
+    rexml (3.3.4)
       strscan
     rouge (3.30.0)
     rubocop (1.25.1)