bump spreadsheet gem

Gemfile.lock

@@ -233,7 +233,7 @@ PATH
   remote: modules/xls_export
   specs:
     openproject-xls_export (1.0.0)
-      spreadsheet (~> 0.8.9)
+      spreadsheet (~> 1.2.6)
 
 GEM
   remote: https://rubygems.org/
@@ -880,7 +880,7 @@ GEM
     shoulda-context (1.2.2)
     shoulda-matchers (3.1.3)
       activesupport (>= 4.0.0)
-    spreadsheet (0.8.9)
+    spreadsheet (1.2.6)
       ruby-ole (>= 1.0)
     spring (2.1.0)
     spring-commands-rspec (1.0.4)
@@ -1067,7 +1067,6 @@ DEPENDENCIES
   posix-spawn (~> 0.3.13)
   prawn (~> 2.2)
   prawn-markup (~> 0.2.1)
-  prawn-table (~> 0.2.2)
   pry-byebug (~> 3.7.0)
   pry-rails (~> 0.3.6)
   pry-rescue (~> 1.5.0)

modules/xls_export/openproject-xls_export.gemspec

@@ -13,5 +13,5 @@ Gem::Specification.new do |s|
 
   s.files = Dir["{app,config,db,lib}/**/*"] + %w(CHANGELOG.md README.md)
 
-  s.add_dependency "spreadsheet", "~>0.8.9"
+  s.add_dependency "spreadsheet", "~>1.2.6"
 end