docs: typo fix (#6729)

https://github.com/vuejs/vue/blob/94512f3e8cee4030a1096121700ed49afab48073/src/platforms/web/entry-compiler.js#L5

Author: meyt

Diff for: packages/vue-template-compiler/README.md

@@ -90,7 +90,7 @@ This is used by default in `vue-loader@>=12` and can be disabled using the [`opt
 
 ---
 
-### compiler.ssrCompileToFunction(template)
+### compiler.ssrCompileToFunctions(template)
 
 > 2.4.0+