Changed feature gate for new PathBuf methods

Feature gate changed to `path_buf_capacity` as per advice from @Mark-Simulacrum

src/libstd/path.rs

@@ -1164,7 +1164,7 @@ impl PathBuf {
     ///
     /// [`with_capacity`]: ../ffi/struct.OsString.html#method.with_capacity
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn with_capacity(capacity: usize) -> PathBuf {
         PathBuf {
             inner: OsString::with_capacity(capacity)
@@ -1404,7 +1404,7 @@ impl PathBuf {
     ///
     /// [`capacity`]: ../ffi/struct.OsString.html#method.capacity
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn capacity(&self) -> usize {
         self.inner.capacity()
     }
@@ -1413,7 +1413,7 @@ impl PathBuf {
     ///
     /// [`clear`]: ../ffi/struct.OsString.html#method.clear
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn clear(&mut self) {
         self.inner.clear()
     }
@@ -1422,7 +1422,7 @@ impl PathBuf {
     ///
     /// [`reserve`]: ../ffi/struct.OsString.html#method.reserve
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn reserve(&mut self, additional: usize) {
         self.inner.reserve(additional)
     }
@@ -1431,7 +1431,7 @@ impl PathBuf {
     ///
     /// [`reserve_exact`]: ../ffi/struct.OsString.html#method.reserve_exact
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn reserve_exact(&mut self, additional: usize) {
         self.inner.reserve_exact(additional)
     }
@@ -1440,7 +1440,7 @@ impl PathBuf {
     ///
     /// [`shrink_to_fit`]: ../ffi/struct.OsString.html#method.shrink_to_fit
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn shrink_to_fit(&mut self) {
         self.inner.shrink_to_fit()
     }
@@ -1449,7 +1449,7 @@ impl PathBuf {
     ///
     /// [`shrink_to`]: ../ffi/struct.OsString.html#method.shrink_to
     /// [`OsString`]: ../ffi/struct.OsString.html
-    #[unstable(feature = "path_buf_alias_os_string_methods", issue = "58234")]
+    #[unstable(feature = "path_buf_capacity", issue = "58234")]
     pub fn shrink_to(&mut self, min_capacity: usize) {
         self.inner.shrink_to(min_capacity)
     }