Bump nanoc from 4.12.20 to 4.12.21

Bumps [nanoc](https://github.com/nanoc/nanoc) from 4.12.20 to 4.12.21.
- [Release notes](https://github.com/nanoc/nanoc/releases)
- [Changelog](https://github.com/nanoc/nanoc/blob/main/nanoc/NEWS.md)
- [Commits](nanoc/nanoc@nanoc-cli-v4.12.20...nanoc-cli-v4.12.21)

---
updated-dependencies:
- dependency-name: nanoc
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile.lock

@@ -42,7 +42,7 @@ GEM
       nanoc-cli (~> 4.11, >= 4.11.14)
       nanoc-core (~> 4.11, >= 4.11.14)
     http_parser.rb (0.6.0)
-    immutable-ruby (0.1.0)
+    immutable-ruby (0.2.0)
       concurrent-ruby (~> 1.1)
       sorted_set (~> 1.0)
     json_schema (0.21.0)
@@ -53,29 +53,29 @@ GEM
       rb-inotify (~> 0.9, >= 0.9.10)
     lumberjack (1.2.4)
     memo_wise (1.8.0)
-    method_source (1.0.0)
+    method_source (1.1.0)
     mini_portile2 (2.8.5)
     multi_json (1.15.0)
-    nanoc (4.12.20)
+    nanoc (4.12.21)
       addressable (~> 2.5)
       colored (~> 1.2)
       nanoc-checking (~> 1.0, >= 1.0.2)
-      nanoc-cli (= 4.12.20)
-      nanoc-core (= 4.12.20)
+      nanoc-cli (= 4.12.21)
+      nanoc-core (= 4.12.21)
       nanoc-deploying (~> 1.0)
       parallel (~> 1.12)
       tty-command (~> 0.8)
       tty-which (~> 0.4)
-    nanoc-checking (1.0.3)
+    nanoc-checking (1.0.5)
       nanoc-cli (~> 4.12, >= 4.12.5)
       nanoc-core (~> 4.12, >= 4.12.5)
-    nanoc-cli (4.12.20)
+    nanoc-cli (4.12.21)
       cri (~> 2.15)
       diff-lcs (~> 1.3)
-      nanoc-core (= 4.12.20)
+      nanoc-core (= 4.12.21)
       pry
       zeitwerk (~> 2.1)
-    nanoc-core (4.12.20)
+    nanoc-core (4.12.21)
       base64 (~> 0.2)
       concurrent-ruby (~> 1.1)
       ddmetrics (~> 1.0)
@@ -103,12 +103,12 @@ GEM
     parallel (1.24.0)
     pastel (0.8.0)
       tty-color (~> 0.5)
-    pry (0.14.1)
+    pry (0.14.2)
       coderay (~> 1.1)
       method_source (~> 1.0)
     psych (5.1.2)
       stringio
-    public_suffix (5.0.4)
+    public_suffix (5.0.5)
     pygments.rb (2.4.1)
     racc (1.7.3)
     rack (3.0.9.1)