Inline PLSQL_BOOLEAN_METADATA into plsql_boolean_metadata

The constant was referenced from exactly one place (`plsql_boolean_metadata`),
so naming the hash literal added an indirection without earning its keep — the
method name already conveys the intent. Inline the hash and drop the constant.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: yahonda

lib/plsql/procedure_call.rb

@@ -1,7 +1,5 @@
 module PLSQL
   class ProcedureCall # :nodoc:
-    PLSQL_BOOLEAN_METADATA = { data_type: "NUMBER", data_precision: 1 }.freeze
-
     def initialize(procedure, args = [], options = {})
       @procedure = procedure
       @schema = @procedure.schema
@@ -634,7 +632,7 @@ def plsql_boolean_to_ruby_value(numeric_value)
       end
 
       def plsql_boolean_metadata(base_metadata)
-        base_metadata.merge(PLSQL_BOOLEAN_METADATA)
+        base_metadata.merge(data_type: "NUMBER", data_precision: 1)
       end
   end
 end