Fix import path for mkcert installation documentation in configuration.mdx

Author: desimone

content/docs/internals/configuration.mdx

@@ -40,7 +40,7 @@ Alternately, you can create individual config files or sets of environment varia
 
 The table contains all config options for Pomerium Core. You can also browse each key using the index on the left.
 
-import InstallMkcert from '@site/content/docs/admonitions/_install-mkcert';
+import InstallMkcert from '@site/content/docs/admonitions/_install-mkcert.md';
 
 ## Service Mode