Fix references to source blocks (#10113)

website/pages/docs/from-1.5/blocks/build/index.mdx

@@ -17,8 +17,8 @@ To use builders in a `build` block you can either:
 
 - Set the `sources` array of string with references to pre-defined sources.
 
-- Define [build-level `source` blocks](/docs/from-1.5/blocks/build/source) or
-  `sources` to use builders. This also allows you to set specific fields.
+- Define [build-level `source` blocks](/docs/from-1.5/blocks/build/source).
+  This also allows you to set specific fields.
 
 `@include 'from-1.5/builds/example-block.mdx'`
 

website/pages/docs/from-1.5/blocks/source.mdx

@@ -19,10 +19,10 @@ block](/docs/from-1.5/blocks/build), for example :
 
 ```hcl
 build {
-  source = [
+  sources = [
     # Here Packer will use a default ami_name when saving the image.
-    "sources.amazon-ebs.example",
-    "sources.amazon-ebs.foo",
+    "source.amazon-ebs.example",
+    "source.amazon-ebs.foo",
   ]
 }
 ```
@@ -32,7 +32,7 @@ set specific source fields.
 
 ```hcl
 build {
-  source "sources.amazon-ebs.example" {
+  source "source.amazon-ebs.example" {
     # Here Packer will use the provided ami_name instead of defaulting it.
     ami_name = "specific"
   }