Set updateable:false explicitly in apex rules.

Currently, this is the default so this is a no-op,
But the default is changing to true.

Bug: 180375550
Test: Treehugger
Merged-In: I68114df38c7c5b6694db8c0a48fd1dce3a2e6572
Change-Id: I25249e6f6c68da85681f545fef1312f1ab0104f4
1 file changed