Update Theano flag doc

doc/library/config.txt

@@ -695,10 +695,9 @@ import theano and print the config variable, as in:
 
 .. attribute:: config.conv.assert_shape
 
-    If False, AbstractConv* ops won't add assert that verify that
-    the user provided shapes are also the one at run time.
-
-    This can speed up compilation time and/or execution time.
+    If True, AbstractConv* ops will verify that user-provided
+    shapes match the runtime shapes (debugging option,
+    may slow down compilation)
 
 .. attribute:: config.dnn.conv.workmem
 

theano/configdefaults.py

@@ -128,8 +128,9 @@ AddConfigVar(
 
 AddConfigVar(
     'conv.assert_shape',
-    "If False, AbstractConv* ops won't add assert that verify that"
-    " the user provided shapes are also the one at run time",
+    "If True, AbstractConv* ops will verify that user-provided"
+    " shapes match the runtime shapes (debugging option,"
+    " may slow down compilation)",
     BoolParam(False),
     in_c_key=False)