[Security] Bump mixin-deep from 1.3.0 to 1.3.1

Bumps [mixin-deep](https://github.com/jonschlinkert/mixin-deep) from 1.3.0 to 1.3.1. **This update includes security fixes.**
- [Release notes](https://github.com/jonschlinkert/mixin-deep/releases)
- [Commits](https://github.com/jonschlinkert/mixin-deep/compare/1.3.0...1.3.1)

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

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@pressbooks/pressbooks-aldine",
-  "version": "1.2.1",
+  "version": "1.5.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -11234,25 +11234,6 @@
         }
       }
     },
-    "mixin-deep": {
-      "version": "1.3.0",
-      "resolved": "https://registry.npmjs.org/mixin-deep/-/mixin-deep-1.3.0.tgz",
-      "integrity": "sha512-dgaCvoh6i1nosAUBKb0l0pfJ78K8+S9fluyIR2YvAeUD/QuMahnFnF3xYty5eYXMjhGSsB0DsW6A0uAZyetoAg==",
-      "requires": {
-        "for-in": "1.0.2",
-        "is-extendable": "1.0.1"
-      },
-      "dependencies": {
-        "is-extendable": {
-          "version": "1.0.1",
-          "resolved": "https://registry.npmjs.org/is-extendable/-/is-extendable-1.0.1.tgz",
-          "integrity": "sha512-arnXMxT1hhoKo9k1LZdmlNyJdDDfy2v0fXjFlmok4+i8ul/6WlbVge9bhM74OpNPQPMGUToDtz+KXa1PneJxOA==",
-          "requires": {
-            "is-plain-object": "2.0.4"
-          }
-        }
-      }
-    },
     "mixin-object": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/mixin-object/-/mixin-object-2.0.1.tgz",

yarn.lock

@@ -6153,8 +6153,8 @@ mississippi@^1.3.0:
     through2 "^2.0.0"
 
 mixin-deep@^1.2.0:
-  version "1.3.0"
+  version "1.3.1"
-  resolved "https://registry.yarnpkg.com/mixin-deep/-/mixin-deep-1.3.0.tgz#47a8732ba97799457c8c1eca28f95132d7e8150a"
+  resolved "https://registry.yarnpkg.com/mixin-deep/-/mixin-deep-1.3.1.tgz#a49e7268dce1a0d9698e45326c5626df3543d0fe"
   dependencies:
     for-in "^1.0.2"
     is-extendable "^1.0.1"