docs/bootc-images.md: small rephrasing

I am sensitive to undefined "this"es.  They require some extra cognitive
work from the reader and may be interpreted in various ways.  Hence,
replace "this" with a more explicit description.

Signed-off-by: Valentin Rothberg <[email protected]>

docs/bootc-images.md

@@ -15,7 +15,7 @@ FROM debian
 RUN apt install kernel
 ```
 
-And get an image compatible with bootc.  Supporting this
+And get an image compatible with bootc.  Supporting any base image
 is an eventual goal, however there are a few reasons why
 this doesn't yet work.  The biggest reason is SELinux
 labeling support; the underlying ostree stack currently
@@ -25,7 +25,7 @@ for any derived layers.
 
 # Building bootc compatible base images
 
-As a corollary to this, the build process
+As a corollary to base-image limitations, the build process
 for generating base images currently requires running
 through ostree tooling to generate an "ostree commit"
 which has some special formatting in the base image.
@@ -34,7 +34,7 @@ However, the ostree usage is an implementation detail
 and the requirement on this will be lifted in the future.
 
 For example, the [rpm-ostree compose image](https://coreos.github.io/rpm-ostree/container/#creating-base-images)
-tooling currently streamlines this, operating just
+tooling currently streamlines creating base images, operating just
 on a declarative input and writing to a registry.
 
 This is how the [Project Sagano](https://github.com/centos/sagano)
@@ -55,8 +55,7 @@ RUN dnf -y install foo && dnf clean all
 
 As an opt-in optimization today, you can also add `ostree container commit`
 as part of your `RUN` invocations.   This will perform early detection
-of some incompatibilities.
-
-However, its usage is not and will never be strictly required.
+of some incompatibilities but is not a strict requirement today and will not be
+in the future.