fix: update dependency gatsby to ^2.15.26 (#17895)

Author: renovate[bot]

starters/blog/package-lock.json

@@ -8,7 +8,7 @@
     "url": "https://github.com/gatsbyjs/gatsby/issues"
   },
   "dependencies": {
-    "gatsby": "^2.15.25",
+    "gatsby": "^2.15.26",
     "gatsby-image": "^2.2.21",
     "gatsby-plugin-feed": "^2.3.13",
     "gatsby-plugin-google-analytics": "^2.1.17",

starters/blog/package.json

@@ -5,7 +5,7 @@
   "version": "0.1.0",
   "author": "Kyle Mathews <[email protected]>",
   "dependencies": {
-    "gatsby": "^2.15.25",
+    "gatsby": "^2.15.26",
     "gatsby-image": "^2.2.21",
     "gatsby-plugin-manifest": "^2.2.18",
     "gatsby-plugin-offline": "^3.0.9",

starters/default/package-lock.json

@@ -13,7 +13,7 @@
     "test": "echo \"Write tests! -> https://gatsby.dev/unit-testing \""
   },
   "dependencies": {
-    "gatsby": "^2.15.25",
+    "gatsby": "^2.15.26",
     "react": "^16.9.0",
     "react-dom": "^16.9.0"
   },

starters/default/package.json

@@ -8,7 +8,7 @@
     "build": "gatsby build"
   },
   "dependencies": {
-    "gatsby": "^2.15.25",
+    "gatsby": "^2.15.26",
     "gatsby-theme-blog-core": "^1.0.0",
     "react": "^16.9.0",
     "react-dom": "^16.9.0"

starters/hello-world/package-lock.json

@@ -8,7 +8,7 @@
     "build": "gatsby build"
   },
   "dependencies": {
-    "gatsby": "^2.15.25",
+    "gatsby": "^2.15.26",
     "gatsby-theme-blog": "^1.0.2",
     "react": "^16.9.0",
     "react-dom": "^16.9.0"