software/theia: pin xtermjs to 4.6.0

When updated to 4.8.1 the cursor "shadow" rendering is incorrect

workaround for https://github.com/eclipse-theia/theia/issues/8158

software/theia/buildout.hash.cfg

@@ -19,7 +19,7 @@ md5sum = 42d21dc3f5d3e57e142eea8e016195f0
 
 [yarn.lock]
 filename = yarn.lock
-md5sum = c8e2d7ebdce31e4a61331317f40c9797
+md5sum = 89d0a4d0c3ae90b9c5c0923b57766f0f
 
 [python-language-server-requirements.txt]
 filename = python-language-server-requirements.txt

software/theia/yarn.lock

@@ -11694,9 +11694,9 @@ xterm-addon-search@^0.5.0:
   integrity sha512-zLVqVTrg5w2nk9fRj3UuVKCPo/dmFe/cLf3EM9Is5Dm6cgOoXmeo9eq2KgD8A0gquAflTFTf0ya2NaFmShHwyg==
 
 xterm@^4.4.0:
-  version "4.8.1"
-  resolved "https://registry.yarnpkg.com/xterm/-/xterm-4.8.1.tgz#155a1729a43e1a89b406524e22c5634339e39ca1"
-  integrity sha512-ax91ny4tI5eklqIfH79OUSGE2PUX2rGbwONmB6DfqpyhSZO8/cf++sqiaMWEVCMjACyMfnISW7C3gGMoNvNolQ==
+  version "4.6.0"
+  resolved "https://registry.yarnpkg.com/xterm/-/xterm-4.6.0.tgz#1b49b32e546409c110fbe8ece0b4a388504a937d"
+  integrity sha512-98211RIDrAECqpsxs6gbilwMcxLtxSDIvtzZUIqP1xIByXtuccJ4pmMhHGJATZeEGe/reARPMqwPINK8T7jGZg==
 
 y18n@^3.2.1:
   version "3.2.1"