gnu: Remove leading article from synopsis.

* gnu/packages/admin.scm (hungrycat)[synopsis]: Remove leading article.
* gnu/packages/cobol.scm (gnucobol)[synopsis]: Likewise.
* gnu/packages/cpp.scm (clipper)[synopsis]: Likewise.
* gnu/packages/crates-graphics.scm (rust-piston-texture-0.8)[synopsis]:
  Likewise.
* gnu/packages/crates-io.scm (rust-alloc-stdlib-0.2, rust-atom-0.3,
  rust-oorandom-11.1, rust-r2d2, rust-scheduled-thread-pool-0.2,
  rust-takeable-option-0.4, rust-ttf-parser-0.12,
  rust-svd-parser-0.9)[synopsis]: Likewise.
* gnu/packages/games.scm (roguebox-adventures)[synopsis]: Likewise.
* gnu/packages/gl.scm (libepoxy)[synopsis]: Likewise.
* gnu/packages/gnome-xyz.scm (arc-theme)[synopsis]: Likewise.
* gnu/packages/haskell-xyz.scm (ghc-cborg-json, ghc-rio)[synopsis]: Likewise.
* gnu/packages/installers.scm (mingw-path)[synopsis]: Likewise.
* gnu/packages/lisp-xyz.scm (sbcl-cl-utilities)[synopsis]: Likewise.
* gnu/packages/lisp.scm (gcl, clisp)[synopsis]: Likewise.
* gnu/packages/maths.scm (coda)[synopsis]: Likewise.
* gnu/packages/ocaml.scm (ocaml4.07-ppx-sexp-message)[synopsis]: Likewise.
* gnu/packages/perl6.scm (perl6-json)[synopsis]: Likewise.
* gnu/packages/python-xyz.scm (python-pari-jupyter, python-markuppy,
  python-febelfin-coda)[synopsis]: Likewise.
* gnu/packages/scheme.scm (mit-scheme)[synopsis]: Likewise.
* gnu/packages/statistics.scm (r-magrittr)[synopsis]: Likewise.
* gnu/packages/terminals.scm (sakura)[synopsis]: Likewise.

gnu/packages/cpp.scm

@@ -1182,7 +1182,7 @@ computation.")
     (native-inputs
      `(("unzip" ,unzip)))
     (home-page "https://sourceforge.net/projects/polyclipping")
-    (synopsis "A polygon and line clipping and offsetting library")
+    (synopsis "polygon and line clipping and offsetting library")
     (description
      "The Clipper library performs line & polygon clipping - intersection,
 union, difference & exclusive-or, and line & polygon offsetting.