[LIGO-47] PascaLIGO: Move block out of case_block alternatives

Problem: In multisig.ligo:48, the case alternative block is
interpreted as empty, while it is not. This happens because
PascaLIGO parser expects to find `fields "statements"` inside
a `case_block`. In practice, if a `case_block` contains a `block`,
statements are deeper in the hierarchy, and get ignored.

Solution: Move "block" option out of the "case_block"
(to _if_clause).

tools/lsp/squirrel/grammar/pascaligo/grammar.js

@@ -363,13 +363,11 @@ module.exports = grammar({
       choice(
         $._instruction,
         $.clause_block,
+        $.block,
       ),
 
     clause_block: $ =>
-      choice(
-        field("block", $.block),
-        seq('{', sepBy1(';', field("statement", $._statement)), '}')
-      ),
+      seq('{', sepBy1(';', field("statement", $._statement)), '}'),
 
     block: $ =>
       choice(
@@ -822,4 +820,4 @@ module.exports = grammar({
     skip: $ => 'skip',
     recursive: $ => 'recursive',
   }
-});
+});