Updates docs for LTI variable expansions

- Changes Canvas.user.globalId and Canvas.root_account.global_id variable docs
- Removed mention of duplicates

Closes INTEROP-5279
flag=none

test plan
- Run rake doc:api
- Review documentation for Canvas.user.globalId and Canvas.root_account.global_id variables

Change-Id: I2d33258be879d5b8ba4a5651150ed4ca25df8d98
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/347686
Reviewed-by: Xander Moffatt <xmoffatt@instructure.com>
QA-Review: Xander Moffatt <xmoffatt@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Product-Review: Alexis Nast <alexis.nast@instructure.com>

doc/api/tools_variable_substitutions.md

@@ -603,7 +603,7 @@ returns the shard id for the current context.
 ```
 1234
 ```
-## Canvas.root_account.global_id [duplicates Canvas.user.globalId]
+## Canvas.root_account.global_id
 returns the root account's global id for the current context.
 
 **Availability**: *always*  
@@ -1047,7 +1047,7 @@ Same as "Canvas.xuser.allRoles", but uses roles formatted for LTI Advantage.
  "http://purl.imsglobal.org/vocab/lis/v2/membership#Instructor",
  "http://purl.imsglobal.org/vocab/lis/v2/system/person#User"
 ```
-## Canvas.user.globalId [duplicates Canvas.root_account.global_id]
+## Canvas.user.globalId
 Returns the Canvas global user_id of the launching user.
 
 **Availability**: *when launched by a logged in user*  

lib/lti/variable_expander.rb

@@ -808,7 +808,6 @@ module Lti
                        -> { Shard.current.id }
 
     # returns the root account's global id for the current context.
-    # @duplicates Canvas.user.globalId
     # @example
     #   ```
     #   123400000000123
@@ -1365,7 +1364,6 @@ module Lti
                        -> { lti_helper.all_roles("lti1_3") }
 
     # Returns the Canvas global user_id of the launching user.
-    # @duplicates Canvas.root_account.global_id
     # @example
     #   ```
     #   420000000000042