Fix Hugo config.toml as valid (#10605)

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Author: tnir

config.toml

@@ -7,7 +7,7 @@ enableRobotsTXT = true
 
 disableKinds = ["taxonomy", "taxonomyTerm"]
 
-ignoreFiles = [ "^OWNERS$", "README[-]+[a-z]*\.md", "^node_modules$", "content/en/docs/doc-contributor-tools" ]
+ignoreFiles = [ "^OWNERS$", "README[-]+[a-z]*\\.md", "^node_modules$", "content/en/docs/doc-contributor-tools" ]
 
 contentDir = "content/en"