Bump mpdf/mpdf from 8.0.14 to 8.0.15 (#2426)

Bumps [mpdf/mpdf](https://github.com/mpdf/mpdf) from 8.0.14 to 8.0.15.
- [Release notes](https://github.com/mpdf/mpdf/releases)
- [Changelog](https://github.com/mpdf/mpdf/blob/development/CHANGELOG.md)
- [Commits](https://github.com/mpdf/mpdf/compare/v8.0.14...v8.0.15)

---
updated-dependencies:
- dependency-name: mpdf/mpdf
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

composer.lock

@@ -1237,16 +1237,16 @@
         },
         {
             "name": "mpdf/mpdf",
-            "version": "v8.0.14",
+            "version": "v8.0.15",
             "source": {
                 "type": "git",
                 "url": "https://github.com/mpdf/mpdf.git",
-                "reference": "ab362c8b11667813487be5d3da64b31c89d9d826"
+                "reference": "d8a5294a6cc2e814c4157aecc8d7ac25014b18ed"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/mpdf/mpdf/zipball/ab362c8b11667813487be5d3da64b31c89d9d826",
+                "url": "https://api.github.com/repos/mpdf/mpdf/zipball/d8a5294a6cc2e814c4157aecc8d7ac25014b18ed",
-                "reference": "ab362c8b11667813487be5d3da64b31c89d9d826",
+                "reference": "d8a5294a6cc2e814c4157aecc8d7ac25014b18ed",
                 "shasum": ""
             },
             "require": {
@@ -1308,7 +1308,7 @@
                     "type": "custom"
                 }
             ],
-            "time": "2021-11-02T20:27:57+00:00"
+            "time": "2021-11-10T08:15:22+00:00"
         },
         {
             "name": "myclabs/deep-copy",