Update asset-generation.md (#998)

Author: oscarlevin

docs/asset-generation.md

@@ -34,7 +34,7 @@ Assets are generated (sometimes using the cache, sometimes skipping it) dependin
 - `pretext build -g` (`pretext build --generate`).  For each asset type in source, we will request it be generated by core regardless of whether the source has changed.  Will copy cached versions of assets where possible.
 - `pretext build -q` (`pretext build --no-generate`).  No assets will be generated (or copied from cache), even if source has changed (or hasn't been successfully generated before).
 - `pretext generate`. Assets of all, or specified, types will be generated, even if source has changed.  Cached versions of individual assets will be copied if possible (CHANGE?).  Identical to `pretext build -g` except it allows to limit by asset type and doesn't call build.
-- `pretext generate -q` (`pretext build --only-changed`). Limit generation of assets to only those that have changed since last call to generate.  Same as `pretext build` except you don't do a build, just generate assets, and can limit to asset type.
+- `pretext generate -q` (`pretext generate --only-changed`). Limit generation of assets to only those that have changed since last call to generate.  Same as `pretext build` except you don't do a build, just generate assets, and can limit to asset type.
 - `pretext generate -f` (`pretext generate --force`).  Generates all assets, even if source has not changed, and does NOT copy assets from cache even if available.
 
 There is also a `pretext generate --clean` that deletes the .cache directory.