Remove environment variables for TRE CA Certificate

This was a bad idea and breaks aws cli.

modules/hic-tre-cert.ps1

@@ -58,19 +58,3 @@ New-Item -Path "C:\Program Files\Mozilla Firefox\" -Name distribution -ItemType
   }
 }
 "@ | Out-File -Encoding ASCII -FilePath "C:\Program Files\Mozilla Firefox\distribution\policies.json"
-
-# This covers both conda and CRAN, but it also overrides their own
-# provided CA chain files. That's probably ok given we don't allow
-# access to the internet.
-[Environment]::SetEnvironmentVariable(
-    "SSL_CERT_FILE",
-    "C:\Tools\hic-tre.dundee.ac.uk.crt",
-    [System.EnvironmentVariableTarget]::User)
-[Environment]::SetEnvironmentVariable(
-    "REQUESTS_CA_BUNDLE",
-    "C:\Tools\hic-tre.dundee.ac.uk.crt",
-    [System.EnvironmentVariableTarget]::User)
-[Environment]::SetEnvironmentVariable(
-    "CURL_CA_BUNDLE",
-    "C:\Tools\hic-tre.dundee.ac.uk.crt",
-    [System.EnvironmentVariableTarget]::User)