Update README.md (#5997)

doc/plutus-core-spec/README.md

@@ -1,10 +1,10 @@
 This directory contains a draft of a version of the Plutus Core specification
 updated so that the language is parametric over a collection of built-in types
 and functions.  It also updates the specification to reflect the fact that
-built-in functions can now be partially applied.  Click
+built-in functions can now be partially applied.  ~Click
 [here](https://ci.iog.io/job/input-output-hk-plutus/master/x86_64-linux.packages.plutus-core-spec/latest/download/1)
 to open a PDF of the most recent version of the specification in the main branch
-of this repository.
+of this repository.~  The link given in the previous sentence currently appears to be broken: would-be readers should build the PDF themselves.  On a Linux system, `make` in the main source directory should do this.
 
 This version is currently restricted to untyped Plutus Core only. We will add a
 specification of a typed version of Plutus Core at a later date.  For the time