Document effect of adopting pantry >= 0.9.2 re Casa prefix

Author: mpilgrem

ChangeLog.md

@@ -201,7 +201,8 @@ Other enhancements:
   precedence over the existing `casa-repo-prefix` key. The latter is deprecated.
   The new key also allows Stack's use of a Casa (content-addressable storage
   archive) server to be disabled and the maximum number of keys per request to
-  be configured. The defaults are unchanged.
+  be configured. The default Casa prefix references https://casa.stackage.org,
+  instead of https://casa.fpcomplete.com.
 * Add option `--progress-bar=<format>` to Stack's `build` command to configure
   the format of the progress bar, where `<format>` is one of `none`,
   `count-only` (only the package count), `capped` (capped to a length equal to

doc/yaml_configuration.md

@@ -639,7 +639,7 @@ Default:
 ~~~yaml
 casa:
   enable: true # Use a Casa server?
-  repo-prefix: https://casa.fpcomplete.com # Unless casa-repo-prefix is set.
+  repo-prefix: https://casa.stackage.org # Unless casa-repo-prefix is set.
   max-keys-per-request: 1280 # Maximum number of keys per request.
 ~~~
 
@@ -659,7 +659,7 @@ deprecated) and has precedence if both keys are set.
 
 Deprecated in favour of [`casa`](#casa), which takes precedence if present.
 
-Default: `https://casa.fpcomplete.com`
+Default: `https://casa.stackage.org`
 
 This option specifies the prefix for the URL used to pull information from the
 Casa server.