rust-index: renamed nodemap error function for rev not in index

The function name was misleading, as the error wording mentions the
nodemap, hence would not be appropriate for missing revisions not
related to a nodemap lookup.

rust/hg-cpython/src/revlog.rs

@@ -603,7 +603,7 b' fn revlog_error(py: Python) -> PyErr {'
     }
 }
 
-fn rev_not_in_index(py: Python, rev: UncheckedRevision) -> PyErr {
+fn nodemap_rev_not_in_index(py: Python, rev: UncheckedRevision) -> PyErr {
     PyErr::new::<ValueError, _>(
         py,
         format!(
@@ -618,7 +618,7 b' fn rev_not_in_index(py: Python, rev: Unc'
 fn nodemap_error(py: Python, err: NodeMapError) -> PyErr {
     match err {
         NodeMapError::MultipleResults => revlog_error(py),
-        NodeMapError::RevisionNotInIndex(r) => rev_not_in_index(py, r),
+        NodeMapError::RevisionNotInIndex(r) => nodemap_rev_not_in_index(py, r),
     }
 }