Remove references to cps_ir

The string `cps_ir` does not show up anywhere else in the SDK repo,
there are no references to or usages of this argument.

Change-Id: Ife5136393cfc026a88aef7b9e00de3e7ad9b13a2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/156688
Auto-Submit: Nate Bosch <nbosch@google.com>
Commit-Queue: Leaf Petersen <leafp@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>

tools/bots/bot.py

@@ -44,7 +44,6 @@ class BuildInfo(object):
   - dart2js_full: Boolean indicating whether this builder will run dart2js
     on several different runtimes.
   - builder_tag: A tag indicating a special builder setup.
-  - cps_ir: Run the compiler with the cps based backend
   """
 
     def __init__(self,
@@ -63,8 +62,7 @@ class BuildInfo(object):
                  arch=None,
                  dart2js_full=False,
                  builder_tag=None,
-                 batch=False,
-                 cps_ir=False):
+                 batch=False):
         self.compiler = compiler
         self.runtime = runtime
         self.mode = mode
@@ -80,7 +78,6 @@ class BuildInfo(object):
         self.dart2js_full = dart2js_full
         self.builder_tag = builder_tag
         self.batch = batch
-        self.cps_ir = cps_ir
         if (arch == None):
             self.arch = 'ia32'
         else: